DECK 15: FINAL 500 - ENTIRE COURSE MIXED

Question 1

What do observational studies and experiments have in common?

Answer 1

In both, you are making OBSERVATIONS. recording data. doing statistical analysis.

Question 2

If you have multiple groups and ask them one question, what Chi-squared test is it?

Answer 2

Test for homogeneity.

Question 3

Give example of confounding variable.

Answer 3

fertilizer A vs B. If you have two tables in a room with tomato plants and and one table gets A and the other gets B, but later you realize that the table with A was near the windows. You say that SUNLIGHT IS A CONFOUNDING FACTOR in that experiment.

Question 4

What are conficence intervals for?

Answer 4

PARAMETER CATCHERS. They are an attempt to say what the true population parameter is.. It is our best guess. “We think that there will be between 8 and 12 inches of snow”

Question 5

What does r 2 tell us? (r-squared)

Answer 5

It tells us the percent of variablility of y that is explained by the model with x.

Question 6

What is “mutually exclusive?”

Answer 6

disjoint. Can’t happen at the same time.

Question 7

Will larger samples reduce BIAS?

Answer 7

No, bias is a systematic flaw, even large samples will still have bias. If you ask more people outside of McDonalds, you still only get answers from people who eat at McDonalds (large samples can reduce error, however)

Question 8

Suppose you are doing a weight loss experiment with 2 diets (A low carb and B low fat), and three medications (1 NUTRI LOSS 2 POUND DROPPER and 3 SLIMMERLY). What is the response variable?

Answer 8

weight loss (pounds)

Question 9

What is a Chi squared model?

Answer 9

A sampling distritubion. If you took a bunch of samples and calculated a bunch of Chi-square statistics, the pile of chi squareds would look like that.

Question 10

What is a quality of SRS that is not a quality of Systematic, Stratified or Clustering?

Answer 10

In an SRS, all groups are possible, and ALL POSSIBLE GROUPS have the same chance of being picked (like all senior male students.).The other methods have lots of impossible groups. SRS has no impossible groups. Example: -Stratified- an impossible group would be all girls (you’re taking some boys and girls)-Clustered- an impossible group would be all girls (each cluster has boys and girls)-systematic- an impossible group would be first 10 people that are right next to each other (you are taking every nth person, so you will skip)

Question 11

Is a confidence interval a PROBABLILITY?

Answer 11

NO

Question 12

When drawing a normal model, what are the PERCENTILES from left to right?

Answer 12

2.5, 16, 50, 84, 97.5

Question 13

How do you find 5 number summary from OGIVE?

Answer 13

Split the y axis into quarters. Shoot out to the right from 0, .25, .50, .75 and 1.00 till you hit the line in the ogive, then go straignt down. Those numbers on the x axis below correspond to the 5 numbers.

Question 14

What type of study would find relationship beween Verbal and Math SAT?

Answer 14

You could take all of the SAT Math and Verbal scores and run a regression and find the r-quared value and linear model. This would be a Retrospective Study.

Question 15

How do you find the median from an OGIVE?

Answer 15

go halfway up the y axis, then shoot across to the curve, then straight down. It’s at the 50th percentile (halfway up)

Question 16

How do you write “A BINOMIAL MODEL WITH p=.35 and n=12?”

Answer 16

B(12, .35) B(N, P)

Question 17

which is response?

Answer 17

y variable, the Vertical axis.. It “responds” to the x

Question 18

In which sampling methods do the subjects have equal chances of being selected?

Answer 18

SRS, Stratified, Clustered, Systematic, and multistage. In all of these, the subjects have an equal chance (but groups have different chances)

Question 19

Gender and Video Game playing are___________ because_______

Answer 19

associated (or not independent) because a higher percentage of males play video games. (think.. It depends on gender)

Question 20

If the p-value is high, (above alpha), how do you write conclusion?

Answer 20

With a p-value this high(show p value < alpha) I fail to reject the null. There is not enough evidence to say that more students like eggs now.

Question 21

Can you prove a null hypothesis true?

Answer 21

NO.. We just fail to reject it.

Question 22

How to find P(at least 1)?

Answer 22

1-P(none)

Question 23

How can you think about the mean and median to remember the difference when looking at a histogram?

Answer 23

mean is balancing point of histogram, median splits the area of the histogram in half.

Question 24

For information purposes, which gives LEAST stem-leaf, histogram or box-whisker?

Answer 24

Box/Whisker, BE CAREFUL. you really don’t know how things are distributed. The box and whisker and fish tank give a very GENERAL look.

Question 25

interpret this 90% confidence interval for avg weight of mice (2.3, 3.5) in ounces

Answer 25

I am 90% confident that the mean weight of mice is between 2.3 and 3.5 ounces

Question 26

How is a paired T test different from a 2 sample mean T test?

Answer 26

A paired test talks about an AVERAGE OF DIFFERENCES from one list, whereas a 2 sample mean t-test talks about a DIFFERENCE OF AVERAGES between two samples.

Question 27

What is undercoverage?

Answer 27

Undercoverage is when a group of the population is not represented in the sample. When the sampling frame isn’t representative.

Question 28

what is disjoint?

Answer 28

can’t be joined . They can’t both happen at the same time! (being over 5 feet and under 4 feet)

Question 29

What values can r be?

Answer 29

from -1 to +1 (r near 0 is WEAK)

Question 30

What is the placebo effect?

Answer 30

When those who get the placebo show improvements, or show the effects of the treatment. This often happens to up 20% of participants!

Question 31

What does Central Limit Theorem Say?

Answer 31

It basically says.. NO MATTER WHAT SHAPE THE POPULATION IS (normal, bimodal, uniform, skewed, crazy.. ) If you make a histogram of a bunch of means taken from a bunch of samples, that histogram will be unimodal and symmetric WITH LARGE ENOUGH SAMPLES.. Close to normal. So.. A nerdy way to say it is: The sampling distribution of means is approximately normal no matter what the population is shaped like. The larger the sample size, the closer to normal. (the normal curve is just a model.. the sampling distribution is close to it, but not it! we use the model anyway!)

Question 32

What is the null model(the sampling distribution) in a 1-sample mean T test?

Answer 32

A pile of means from a bunch of samples.

Question 33

Can you stratify in an experiment?

Answer 33

NO. stratification is a sampling method, blocking is method used in experiments. They are similar ideas.

Question 34

If you want to find percentile for a value, what do you put into normcdf (? ?)

Answer 34

find z score for value, and then normcdf (-999, Zright) like going from negative infinity up to the z score

Question 35

What does r tell us?

Answer 35

The direction (+/-) and how strong a LINEAR relationship is between two QUANTITATIVE variables (when linear)

Question 36

How are we manipulating the environment differently in experiments and studies?

Answer 36

No manipulation or treatments in an observational study. You only manipulate environment in an experminet.

Question 37

What is BIAS in sampling?

Answer 37

A systematic FLAW in your method.

Question 38

Which is explanatory variable?

Answer 38

the x the horizontal axis. it “explains” what happens to y

Question 39

Use the following words in one sentence: population, parameter, census, sample, data, statistics, inference, population of interest.

Answer 39

I was curious about a population parameter, but a census was too costly so I decided to choose a sample, collect some data, calculate a statistic and use that statistic to make an inference about the population parameter (aka the parameter of interest).

Question 40

What is the problem with convenience sampling?

Answer 40

The sample may not be representative as it is not randomized to include every type of person. Friends and family are convenient but they likely share similar opinions and thus the sample is not representative of a population.

Question 41

What is the mode?

Answer 41

the most common, or the peaks of a histogram. We often use mode with categorical data

Question 42

Give example of factors and levels

Answer 42

Factor: medication. Levels: 50mg, 100mg and 200mg.

Question 43

What is difference between population of interest and parameter of interest?

Answer 43

Population is the WHO (subjects you measure, beads people) Parameter is the actual number you want (like % of or AVG)

Question 44

What is the five number summary?

Answer 44

min, Q1 , Q2(median), Q3 and max

Question 45

What percent of the data is between Q1 and Q3?

Answer 45

50%

Question 46

How can the WORDING of the question lead to response bias

Answer 46

Words or phrases that impact your feelings tend to influence responses. Look for “devastating, horrific, wonderful etc.” Sometimes there is a background story like “Many americans lose jobs to illegal aliens every year, do you feel this is fair”

Question 47

What is stratified sampling?

Answer 47

When you break the population into groups with similar attributes and randomly select from each strata.

Question 48

Compare population to sample

Answer 48

populations are generally large, and samples are small subsets of these population. We take samples to make inferences about populations. We use statistics to estimate parameters.

Question 49

What is the difference between quantitative and categorical variables?

Answer 49

Quantitative variables are numerical measures, like height and IQ. Categorical are categories, like eye color and music preference

Question 50

What is a probability distribution?

Answer 50

A table or graph showing all of the probabilites of certain occurances. THE PROBABILITIES HAVE TO ADD TO ONE!

Question 51

How is r calculated?

Answer 51

r = sum(Z x Z y ) / (n-1) it is the sum of rectangle areas on the standardizes Z axes

Question 52

What is a representative sample?

Answer 52

A sample that looks like the population. It has similar characteristics.

Question 53

A bag has 3 red chips and 4 blue chips.. WTPT you grab a red first, then put it back in and then grab a red again?

Answer 53

3/7 * 3/7 = 9/49 (indep events)

Question 54

What is the null for a chi squared GOF test?

Answer 54

The distribution fits [the expected distribution]

Question 55

Why randomize in an experiment?

Answer 55

To reduce confounding variables (and bias).

Question 56

Think of the minimum value, the mean and the standard deviation, what is impacted by shifting (adding a constant)

Answer 56

adding a value shifts the entire histogram to the right, so the min and the mean will increase by that amount, BUT THE SD WILL NOT CHANGE.

Question 57

what does influential mean?

Answer 57

It impacts the SLOPE. It means that the point, when added or removed to data, will influence the SLOPE. Generally these are outliers in the x direction. Far left or right.

Question 58

When your sampling frame is different from the population, then you risk ____

Answer 58

undercoverage

Question 59

What is the standard sampling method?

Answer 59

A Simple Random Sample (SRS) is our standard. Every possible group of n individuals has an equal chance of being our sample. That’s what makes it simple. Put the names in a hat.

Question 60

Example of response bias

Answer 60

A teenager goes to the doctor’s office with their parents. The doctor asks the teen if they vape. The teen may say “no” because their parent’s are there, even though they do vape.

Question 61

What should we look for in resid plot?

Answer 61

Curve or pattern. Also, it should have equalish scatter from left to right It should look RANDOM

Question 62

Can there be a correlation between grade and music preference?

Answer 62

No, music preference is categorical. There is an association, however.

Question 63

Compare data to parameters

Answer 63

Data is each little bit of information collected from the subjects?. They are the INDIVIDUAL little things we collect? we summarize them by, for example, finding the mean of a group of data. If it is a sample, then we call that mean a “statistic” if we have data from each member of population, then that mean is called a “parameter”

Question 64

What does normcdf do?

Answer 64

It gives you the area under the normal curve between any two z scores , or percent between 2 values if you use the shortcut normcdf (low, high, mean , sd)

Question 65

Which is more sensitive to outliers and skewed? Mean, median. Sd or IQR?

Answer 65

Mean and SD are most influenced by outliers. median and IQR are RESISTANT, RESILIENT, ROBUST!!

Question 66

What is extrapolation?

Answer 66

Making predictions outside of the x values you have.

Question 67

using calculator: suppose 30% of dogs have fleas. WTPT first dog with fleas was the fifth you checked?

Answer 67

not, not, not, not, yes. .7x.7x.7x.7x.3orgeopdf (.30, 5

Question 68

What is a confidence interval?

Answer 68

it is a parameter catcher.. Like a fishing net. We stand at our statistic, and reach up and down a margin of error, and hope to CATCH the parameter? sometimes we do, sometimes we don’t? but we never know.. Mooo hooo hooo haaaa haaa haaa (evil laugh)

Question 69

4 INGREDIENTS TO EXPERIMENTS

Answer 69

Compare, control , randomization, replication (and BLOCKING when you need to)

Question 70

A 4 year high school of 2000 students, sampling 40 high students : Describe a systematic sample

Answer 70

Get an alphabetical list of all of the students, 2000/40=50. Randomly choose one of the first 50 students and then every 50th student after that.

Question 71

How is BIAS different from SAMPLING error

Answer 71

Bias is a systematic flaw in your sampling method. Sampling error is always present even with the best methodology.

Question 72

What is the mean and mode of a chi squared model? What is the 5% cutoff chi-squared?

Answer 72

The mean is the degrees of freedom and the mode is df-2. The cutoff is at 1.5df+3.

Question 73

notation: what is p

Answer 73

true population proportion (percent in the population)

Question 74

describe a scatterplot’s strength?

Answer 74

give the r value (if straight), or say “tightly packed loosely packed”

Question 75

If you want to calculate % above a value, what do you put into normcdf(? ?)

Answer 75

find z score for value, and then normcdf (Z left, 999)

Question 76

In order to reject a null hypothesis, you need ___________

Answer 76

evidence

Question 77

What are the three chi-squared models?

Answer 77

goodness of fit, test for homogeneity, test for independence

Question 78

What are the two types of observational studies?

Answer 78

Retrospective, and Prospective

Question 79

what happens if you multiply all of a data set by a constant? Think of an example

Answer 79

it is scaled Both center and spread are impacted. Mean/ median/ stand dev/ iqr/ quartiles all multiplied by that constant. Center, spread and all individual values are changed. Consider 1,2,3,4,5 mean of 3 and range of 4. Now multiply by 3: 3,6,9,12,15 and you get a mean of 9 and a range of 12. both multiplied by three.

Question 80

What percentile is Q3?

Answer 80

75th

Question 81

If you are tasting soup.. Then the flavor of each individual thing in the spoon is the ________, the entire spoon is a ______.. The flavor of all of that stuff together is like the _____ and

Answer 81

If you are tasting soup. Then the flavor of each individual thing in the spoon is DATA, the entire spoon is a SAMPLE. The flavor of all of that stuff together is like the STATISTIC, and you use that to MAKE AN INFERENCE about the flavor of the entire pot of soup, which would be the PARAMETER. Notice you are interested in the parameter to begin with. that is why you took a sample.

Question 82

What symbols do we use for population proportion (%) and sample proportion (%)?

Answer 82

p for population and p-hat for sample

Question 83

What is the main purpose of a placebo ?

Answer 83

to see how the environment impacts the subjects. How do all of the other factors impact the subject.

Question 84

using calculator: suppose 30% of dogs have fleas. WTPT less than 4 out of 10 have fleas?

Answer 84

less than 4 is the same as 3 or less.binocdf (10, .30, 3)

Question 85

What is sampling error?

Answer 85

same as sampling variability.. The natural variability between STATISTICS.. NOT DATA!!! . We call it error EVEN THOUGH YOU MADE NO MISTAKES!!!

Question 86

Does high r squared mean a good model?

Answer 86

CHECK SCATTER FIRST.. Make sure model “FITS” the data. You should check your scatterplot and residuals plot to make sure model is appropriate and no outliers present then it means something So YES, but after you check the resids.

Question 87

the (n over k) thing has a (5 over 2), how would you do it? What is it called?

Answer 87

Also known as “5 choose 2” or “5 C 2”.. 5! / 3!2! (notice the bottom two add to the top)

Question 88

notation: what is mu

Answer 88

true population mean (average)

Question 89

you fail to reject when ____________ evidence

Answer 89

you fail to reject when you DON’T HAVE EVIDENCE

Question 90

What is a standard error?

Answer 90

The typical, or expected, error. The spread of a pile of stats. It is how far off you are expecting your statistic to be from the parameter. It is calculated like the standard deviation, but we are using sample statistics.. We don’t know the true parameters, so we estimate with statistics adding error to our calculation

Question 91

What is the general formula for ALL CONFIDENCE INTERVALS?

Answer 91

STAT +/- CRIT SE

Question 92

What is probability first success is on 7th try?

Answer 92

qqqqqq p (q^6*p). (this is a GEO prob)

Question 93

Suppose you are doing a weight loss experiment with 2 diets (A. low carb and B. low fat), and three medications (1. NUTRI LOSS, 2. POUND DROPPER and 3. SLIMMERLY). How many treatment groups would there be?

Answer 93

there would be 6: A1, A2, A3, B1, B2, B3

Question 94

what is another name for alpha level?

Answer 94

a significance level

Question 95

N ( ?1 , ?2 ) what does this mean?

Answer 95

it means NORMAL models centered at 1 With a standard deviation of 2

Question 96

What’s up with extrapolation? Is it OK?

Answer 96

Not ideal. Sometimes it’s all you can do, but state CAUTION.

Question 97

Height and weight has an r value of 0.7. You would expect a person with a height that is 2 st. dev above the mean in height to have a weight that is only___St. Dev above the mean weight.

Answer 97

only 1.4 S.D above the mean for weight. (for each SD in the x direction you change r SD in the y direction)

Question 98

geocdf

Answer 98

(p,x) . Probability of the FIRST SUCCESS being ON OR BEFORE the Xth trial.

Question 99

What is a Z score?

Answer 99

The number of standard deviaiton away from the mean

Question 100

What is the median?

Answer 100

the middlest number, it splits area in half (always in the POSITION (n+1)/2 )

Question 101

A 4 year high school of 2000 students, sampling 40 high students: Describe a convenience sample

Answer 101

Ask the first 40 students coming to the locker rooms after school. This is problematic because athletes may not have the same preferences as non athletes.

Question 102

Association and Independence. How are they related?

Answer 102

Variables are either independent or associated. Meaning: if one impacts the other then we say there is an association. If not, Then they are independent.

Question 103

Compare DATA-STATISTIC-PARAMETER using quantitative example

Answer 103

Data are individual measures, like how long a person can hold their breath: ?45 sec, 64 sec, 32 sec, 68 sec.? That is the raw data. Statistics and parameters are summaries like ?the average breath holding time in the sample was 52.4 seconds? and a parameter would be ?the average breath holding time in the population was 52.4 seconds?

Question 104

what is leverage?

Answer 104

Far right or left from the middle. leverage just means it is far away from x-bar Some leverage points are not influential if they go along with the flow of the scatter.

Question 105

how do you interpret y intercept?

Answer 105

The model predicts that if there were no [x stuff] this is how much [y stuff] you’d have

Question 106

What is the difference between a sample and a census?

Answer 106

With a sample, you get information from a small part of the population. In a census, you get info from the entire population. You can get a parameter from a census, but only a statistic from a sample.

Question 107

using calculator: suppose 30% of dogs have fleas. WTPT exactly 5 out of 12 have fleas?

Answer 107

binopdf(12, .30, 5)

Question 108

What is a point estimate?

Answer 108

Your statistic, the sample p-hat or your x-bar. Your best guess. What you got in your sample. It is in the middle of the interval.

Question 109

What is the line that you plot?

Answer 109

IT IS A MODEL! It is the LSRL and it is the model we are talking about

Question 110

How are statistics and parameters different?

Answer 110

A statistics is a numerical description of a sample, and a parameter is a description of a population. The difference between these is called ERROR (sampling error).

Question 111

How do you find a certain percentile on an OGIVE?

Answer 111

Start at the % on the Y axis.. travel horizontally to the right until you hit the line, then straight down to the X axis. That data value is the percentile.

Question 112

does correlation mean causation?

Answer 112

NO WAY DUDE

Question 113

What is the “ large enough sample” condition for Chi Square?

Answer 113

Make sure that there are at least 5 in each expected cell.

Question 114

How are voluntary and convenience samples similar

Answer 114

With voluntary, people choose them selves, with covenience, the people are just chosen by researcher, neither uses randomness and both are prone to BIAS.

Question 115

How can you match boxplots to histograms?

Answer 115

USE THE FISH TANK METHOD!

Question 116

Which calculator function gives you a z score?

Answer 116

invnorm(%ile),

Question 117

What is a factor? give example

Answer 117

DIET PLAN would be a factor and levels could be: low carb, low fat, and no diet

Question 118

How are we making inferences differently in experiments vs studies?

Answer 118

In observaional studies, you make and inference about the population, in an experiment you make an inference about a treatment.

Question 119

What is the null model (the sampling distribution) in a 1-proportion Z test?

Answer 119

A pile of proportions (%) from a bunch of samples.

Question 120

If you have one group and ask them one question, what type of chi-squared test is it?

Answer 120

Goodness of fit test.

Question 121

using calculator: suppose 30% of dogs have fleas. WTPT exactly 7 or less out of 20 have fleas?

Answer 121

binocdf (20, .30, 7)

Question 122

What percent of the data is above Q3?

Answer 122

25%

Question 123

A 4 year high school of 2000 students, sampling 40 high students: Describe a cluster sample

Answer 123

Imagine that all of art classes have 10 students and they are mixed with fr, so, jr and srs. You would randomly choose 4 classes and survey everyone in each of the 4 classes.

Question 124

DEGREES OF FREEEDOM: one sample t, two sample T, regression, chi square gof, chi square hom/indep

Answer 124

one sample t: n-1two sample t: calc or smaller n-1regression: n-2Chi square GOF: cells-1CHi square hom/indep: ROW-1 x COL-1

Question 125

What is the law of averages?

Answer 125

a misinterpretation of the law of large numbers. Using this law, if you flipped 4 heads in a row, you’d expect the next one to be a tails because it should even out in the long run, as if the coin remembers that it “owes you” something NOT TRUE

Question 126

How do you undo squares or cubes? like if you have x 2 = stuff or x 3 = stuff

Answer 126

^ 1/2 or ^ 1/3 (raise stuff to these powers to get x)

Question 127

What is statistical inference?

Answer 127

Using a statistic to infer something about a parameter.. Basically, using a sample to say something about a population.

Question 128

What is the null model (the sampling distribution) in a chi squared test?

Answer 128

a pile of chi-squared statistics calculated from a bunch of samples

Question 129

What percent of the data is between Q1 and Q3?

Answer 129

the middle 50%. That is the IQR

Question 130

What is a residual?

Answer 130

Vertical distance to the LSRL. ACTUAL-PREDICTED, A-P, like this class AP (get it?) Take y data found and from that, subtract the y you get from plugging the x into the model (equation).

Question 131

What’s the difference between a prospective and a retrospective study?

Answer 131

A retrospective study takes a group and looks back at its history while a prospective study watches a group for a period of time and records the data along the way into the future.

Question 132

What is alpha?

Answer 132

It is the rejection threshold. You reject p-values below it.. It is how willing you are to make a Type 1 error? alpa=P(Type I error)

Question 133

A 4 year high school of 2000 students, sampling 40 high students: Since ALL GROUPS (samples) are possible and equally likely, show some groups that you could get randomly from and SRS that would not be representative of the entire school.

Answer 133

all female, all freshmen, all seniors, all athletes.. these could happen in an SRS (but they are not likely to)

Question 134

notation: what is p-hat

Answer 134

sample proportion (percent in our sample)

Question 135

What is a parameter?

Answer 135

A numerical summary of a population. Like a mean, median, range? of a population

Question 136

4 ingredients: What is “control?”

Answer 136

You want to control the environment as best as you can so that the only difference between groups is the treatment, and the treatment only. Everything else should be similar.

Question 137

What is the difference between response bias and nonresponse bias?

Answer 137

Response is when the person’s response is influenced by the question or questioning method (like if a parent asks if you use drugs, as opposed to a friend. there is only one answer to this, but one might respond differently to them), non response is is when the people who don’t respond might have different opinions/views than the people who did.

Question 138

Control group vs Experimental group

Answer 138

The experimental group gets the treatment (pill, fertilizer) while the control gets placebo or nothing. You compare the experimental group to control group.

Question 139

What is difference between completely randomized and random block design?

Answer 139

Completely randomized takes all units and puts them in a hat and randomly chooses treatments, blocked puts them all in different hats first (blocks) and then chooses

Question 140

What percent of the data is below the median?

Answer 140

50%

Question 141

CONDITIONS: What are the three conditions that you have to check with pretty much every inference procedure (every test and every interval)

Answer 141

1. Randomly chosen sample (or assigned treatment). Circle the word random or explain why you think it is. 2. Sample size is less than 10% of the population. Show that 10n is less than N. Example, for 50 students, write 10(50)=500 is less than all students.3. Nearly normal (or large enough sample)- this differs based on the type of data and test.

Question 142

What is the difference between a bar chart and a histogram

Answer 142

bar charts are for categorical data (bars don’t touch) and histograms are for quantitative data (bars touch)

Question 143

What is categorical data?

Answer 143

The actual individual category from a subject, like “blue” or “female” or “sophomore”

Question 144

What is the difference between quantitative and categorical data?

Answer 144

The data is the actual gathered measurements. So, if it is eye color, then the data would look like this “blue, brown, brown, brown, blue, green, blue, brown? etc.” The data from categorical variables are usually words, often it is simpy “YES, YES, YES, NO, YES, NO” If it was weight, then the data would be quantitative like “125, 155, 223, 178, 222, etc..” The data from quantitative variables are numbers.

Question 145

is r sensitive to outliers?

Answer 145

yes. A single outlier can make it seem like there is a relationship ( if way out in x direction), or even seem like there is no relationship.

Question 146

Can you accept a null hypothesis? Can you say “keep the null?”

Answer 146

Never accept a Ho, don’t keep the Null. simply “FAIL TO REJECT THE NULL”

Question 147

A 4 year high school of 2000 students, sampling 40 high students: Explain how stratifying has “impossible groups”

Answer 147

You couldn’t get all freshmen in your sample

Question 148

What point is on every regression line?

Answer 148

the mean-mean point. (x bar, y bar). This point is generally not one of the points on the scatterplot. Usually none of the scatterplot points are on the regression line.

Question 149

What is the “mean of a random variable?”

Answer 149

The expected value sum of probs times values

Question 150

What’s the difference between stratified and cluster sampling?

Answer 150

Stratified- you divide the population up into groups with similar traits, called strata (homogeneous groups) and randomly choose a few from each strata.

Question 151

How do you interpret slope?

Answer 151

For an increase of 1 [unit of x] there is an (increase/decrease) of [SLOPE] [units of y]. You can write “SLOPE UNITS Y/ ONE UNITS X” to help

Question 152

when do you need crits?

Answer 152

in confidence intervals (and old fashioned hyp tests.. We look at Z to see if greater than crit.)

Question 153

What is the mode?

Answer 153

the peaks of a histogram (the humps). or with categorical data, the most popular category

Question 154

What is “statistically significant?”

Answer 154

When our sample statistic is so far away from what we were expecting that we don’t think that it was due to random sampling error. Then is statistically significant. When p-value is below the alpha, we say “statistically significant”.. Low p-values are statistically significant.

Question 155

To make a survey to tell of a restaurant is good, would you ask the people coming out of the restaurant?

Answer 155

People at the restaurant are probably there because they already like it. If you asked the question “Is this your first time dining here?” and if they say “yes” you survey them, that would be a better method. But then again.. the people wouldn’t go into an Italian restaurant if they didn’t like that type of food.

Question 156

Who can be blinded? ( two groups)

Answer 156

1. Subjects (and dog owners..). The poeple getting treatment and 2. administrators. Those delivering treatments and assessing effectiveness of treatments.

Question 157

what is a probability model?

Answer 157

a list of all possible values of random variable with respective probabilities. The probabilities should add to 1! Normal model is one

Question 158

If you want to find % below a value, what do put into normcdf (? ?)

Answer 158

find z score for value, and then normcdf (-999, Zright) or shortcut normcdf(-99999, value, mean, sd)

Question 159

What is the variance?

Answer 159

The average squared distance to the mean. Or the SD2 (It is the SD before you take the square root, so it is the stuff under the radical in the formula)

Question 160

using calculator: suppose 30% of dogs have fleas. WTPT AT LEAST ONE OUT OF 10 has fleas?

Answer 160

1-none= 1-.7^10or1-binopdf( 10, .30, 0)or1-binocdf( 10, .30, 0)

Question 161

Does r 2 tell direction?

Answer 161

NO r 2 is always positive, so you can’t use it to see if the relationship is negative.

Question 162

Give example of correlation without causation and explain the lurking variable.

Answer 162

Ski accidents are higher on days with more hot chocolate sales, therefore, hot chocolate must cause ske accidents. (lurking variable: the number of people on the mountain). What is happening is that on days when the mountain is crowded, there are more hot chocolate sales and more ski accidents. So the population on the mountain is causing both to rise and fall together.

Question 163

What do you know about the sign of r and the slope of the regression?

Answer 163

they have the same sign. Both will be positive or both will be negative.

Question 164

Does the IQR capture 68% of the data?

Answer 164

NO. it catches the middle 50%.

Question 165

If I take a random sample 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and the average number of pickles was 9.5, then 9.5 is considered a _______?

Answer 165

statistic. (t is a summary of a sample.)

Question 166

When do you know it is GOF test?

Answer 166

When you have ONE ROW or ONE COLUMN… then it gives you a ratio , like 1:2:5 or it gives you expected percents.

Question 167

Another name for “skewed right” is

Answer 167

positively skewed

Question 168

what does “95% confidence” in a 95% confidence interval mean? (explain the confidence level)

Answer 168

It means if we took a ton of samples, and made confidence intervals from each of them,ABOUT 95% of the intervals would contain the parameter, 5% would not.

Question 169

If you are doing a 2 tailed test with alpha=.05.. What confidence interval goes with that?

Answer 169

95% confidence interval (there is .025 in each tail)

Question 170

are there any normal samples?

Answer 170

no, nothing is normal, just normalish. The only normal thing is the model we use.

Question 171

which calculator function gives you a percent?

Answer 171

normcdf(Z left, Z right)

Question 172

What’s a useful alternative when you can’t run an experiment? What are they useful forms of this, and how do you preform them respectively?

Answer 172

An alternative of an experiments could be an observational study. t.

Question 173

using calculator: suppose 30% of dogs have fleas. WTPT no more than 8 out of 15 have fleas?

Answer 173

not more than 8 is the same as 8 or less.binocdf(15, .30, 8)

Question 174

What is data?

Answer 174

Any collected information. Generally each little measurement? Like, if it is a survey about liking porridge? the data might be ?yes, yes, no, yes, yes? if it is the number of saltines someone can eat in 30 seconds, the data might be ?3, 1, 2, 1, 4,3 , 3, 4?

Question 175

Computer ouput: What does “constant” mean?

Answer 175

It is the y intercept

Question 176

Can you eliminate sampling error?

Answer 176

Only if you take a census. Larger samples have less error.

Question 177

What is the other conditions for regression inference?

Answer 177

Random residuals (equal random scatter, no pattern).

Question 178

Give example of incorrectly using the word “correlation”

Answer 178

“there is a correlation between gender and video game playing” This person should say “association.” You can’t say correlation because gender is categorical.

Question 179

what is a clear example of the medians resiliance and when you would use the median instead of the mean?

Answer 179

(change just the top value). Imagine if we asked eight people how much money they had in their wallet. We found they had {1, 2, 2, 5, 5, 8, 8, 9}. The mean of this set is 5, and the median is also 5. You might say “the average person in this group had 5 bucks.” But imagine the same group the next week, but one of them just got back from the casino and the dist was (1, 2, 2, 5, 5, 8, 8, 9000}, in this case, the median would still be 5, but the mean goes up to over 1000. Which number better describes the amount of money the average person in the group this time? 5 bucks or 1000 bucks? I think 5 is a better description of the average person in this group and the 9000 is simply an outlier.

Question 180

How can you turn OGIVES into histograms?

Answer 180

RECTANGLE DROP! (bin drop)

Question 181

What symbols do we use for population mean and sample mean?

Answer 181

Mu for population mean, xbar for sample mean.

Question 182

How do you find outliers in regression?

Answer 182

they don’t follow the “flow” (pinky trick, cover with you pinky.. Then uncover.. Does it follow the flow?)

Question 183

notation: what is p - p

Answer 183

true difference between two population proportions (percents).

Question 184

If I take a random sample of 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and I do this because I want to know the true average number of pickles on a bur

Answer 184

parameter, a one number summary of the population. The truth. AKA the parameter of interest.

Question 185

when is data “paired”

Answer 185

when you have 2 measurements of the same variable on the same subject (or matched subjects)

Question 186

using calculator: suppose 30% of dogs have fleas. WTPT first dog with fleas was ON OR BEFORE the fifth you checked?

Answer 186

geocdf (.30, 5)

Question 187

When we say “statistics vary” or the “variablility of statistics” are we talking about data from an individual?

Answer 187

NO. we are stating that summaries of samples (statistics) will vary from sample to sample. Statistics from one sample will differ from statistics from another sample and they will also differ from the parameters. The distance your statistic is from the parameter is called the ERROR. Larger samples will give piles of statistics that will be narrower (less variability).

Question 188

When you are doing PAIRED or MATCHED or BLOCKED tests.. What are you finding?

Answer 188

The average difference.. You are doing 1 sample procedures on a NEW THIRD LIST OF DIFFERENCES

Question 189

what is df for chi squared homogeneity or independence?

Answer 189

(rows-1)(columns - 1) (remove a column and row.. Count boxes)

Question 190

What is the expected value?

Answer 190

The mean What you’d AVERAGE if you played the game A LOT!!!!!!!!!

Question 191

Compare DATA-STATISTIC-PARAMETER using categorical example

Answer 191

Data are individual measures? like meal preference: ?taco, taco, pasta, taco, burger, burger, taco?? Statistics and Parameters are summaries. A statistic would be ?42% of sample preferred tacos? and a parameter would be ?42% of population preferred tacos.?

Question 192

What is statistically significant?

Answer 192

When an observed difference is too odd for us to believe that it is likely to have occurred naturally (or just randomly). Basically it is Statistically Significant when we don’t think it happened randomly. when you think “something’s up” or “something’s fishy”

Question 193

what is the law of large numbers?

Answer 193

guarantees that in the long run.. The relative frequency settles down to true probability.. (you’ll have 50% heads after an infinite number of coin flips with a fair coin)

Question 194

How do you undo an ln (natural log) when solving? ex: ln x = stuff or: ln x = m

Answer 194

e stuff or e m

Question 195

An unbiased sampling method will eliminate error

Answer 195

No, error is always there. Error is not a mistake.

Question 196

You own a bike shop and order your tires from 2 companies (A and B). You order 80% from A and 20% from B. 1% of the tires from A are defective, while 4% from B are defective What is the probability that a defective tire is from company A? How would you do this?

Answer 196

Tree diagram. Split up by company first, then use conditionals. A BAD (.8)(.01)= .008A GOOD (.8)(.99)= .792B BAD (.2)(.04)= .008B GOOD (.2)(.96)= . 192It seems that .008/(.008+.008) or 50% are bad

Question 197

What is variability?

Answer 197

Differences? how things differ. There is variability everywhere.. We all look different, act different, have different preferences? Statisticians look at these differences.

Question 198

How do you write conclusion if you reject?

Answer 198

With such a low p-value, (p-value < alpha) I reject the null hypothesis. There is strong evidence that the proportion of students who eat rice has changed.

Question 199

Example of undercoverage

Answer 199

You only ask people who go to Home Depot about their views on school lunches.

Question 200

binopdf

Answer 200

(n,p,x) .. Probability of exactly X successes in N trials. (PARTICULAR probability)

Question 201

if you mult or divide the x’s or y’s (shift/scale) does r change?

Answer 201

no. the strength remains the same. (If you log or square it, it will change, but just adding or multiplying won’t change it)

Question 202

If I take a random sample of 20 hamburgers from FIVE GUYS and count the number of pickles on a bunch of them? and one of them had 9 pickles, then the number 9 from that burger would be calle

Answer 202

a datum, or a data value.

Question 203

mean/SD/median/IQR. How do I know which ones to use?

Answer 203

when unimodal and symmetric, mean and sd. If skewed or outliers? Median and IQR. If bimodal? Talk about the MODES

Question 204

If the distribution is skewed (or outliers/not symmetric) what would you use for center and spread statistics?

Answer 204

Median (center) and IQR (spread)

Question 205

How do we use representative samples in experiments and studies?

Answer 205

You don’t need a representative sample in an experiment. You are not making inferences about a population, just about a treatment.

Question 206

Does a high r value mean anything? (can it look strong, but not be?)

Answer 206

Sure. It can. It tells you strength of LINEAR relationship. BUT CHECK THE SCATTER. One outlier or typo can make it look STRONG.

Question 207

How do you interpret slope EQUATION? rSy/Sx

Answer 207

for each increase of 1 st dev in x direction, you go r st dev in y direction. 2st dev in x, you go 2r st. dev in y. 3st dev in x, you go 3r st. dev in y.

Question 208

How is a confidence interval made?

Answer 208

statistic +- margin of error. Statistic +- (crit * s.d ). Stand at the statistic, reach out up and down a margin of error, and hope that you catch the parameter.

Question 209

WHat is the null model (the sampling distribution) in a paired T-Test?

Answer 209

A pile of average differences. Remember that in a paired test, you are getting an individual differenc from each pair of data, then finding the average of differences.

Question 210

Give a quick example of associated variables

Answer 210

A higher percentage of boys play video games than girls so we say “gender and video game playing are associated” or “gender and video game playing are not independent”

Question 211

notation: what is z*

Answer 211

critical z, how many SE you are reaching up and down in a confidence interval for proportions

Question 212

What is the null for a 2 prop Z?

Answer 212

p1=p2 OR. p1-p2=0, there is no diff

Question 213

What percent of the data is above Q3?

Answer 213

25%

Question 214

What is the difference between a parameter and a statistic?

Answer 214

BOTH ARE A SINGLE NUMBER SUMMARIZING A LARGER GROUP OF NUMBERS?. But pppp parameters come from pppp populations? sss statistics come from ssss samples.

Question 215

What happens to a pile of statistics if you take larger samples?

Answer 215

All of the x-bars or all of the p-hats will get closer to eachother, and closer to the parameter ( mu or p)

Question 216

Interpret residual: Points above the line/positive resid

Answer 216

“the model underpredicted” or “actual performance was above the expected performance

Question 217

What is the differnce between standard error and standard deviation?

Answer 217

Standard error is the typical distance a STATISTIC is from the mean in a sampling distribution (pile of a bunch of sample’s statistics) and Standard Error is the typical distance a DATUM is from the mean in a pile of raw data.

Question 218

What is the “nearly normal” condition for proportions? (aka large enough sample)

Answer 218

np>10 and nq>10. actually Show this calculation

Question 219

What symbols do we use for population mean and sample mean?

Answer 219

Mu for population mean, xbar for sample mean.

Question 220

A bag has 3 red chips and 4blue chips.. WTPT you grab a blue then a red? (without replacing)

Answer 220

4/7 * 3/6 (notice that there were only 6 in the bag)

Question 221

When we say the average teenager are we talking about mean

Answer 221

It depends, if we are talking height, it might be the mean, if we are talking about parental income, we’d probably use the median, if we were talking about music preference, we’d probably use the mode to talk about the average teenager.

Question 222

How are power and alpha related?

Answer 222

they go up and down together, unless you get a larger sample, then power increases. You can set the alpha to anything you want.

Question 223

A bag has 3 red chips and 4 blue chips.. WTPT you reach in and grab 2 reds?

Answer 223

3/7 * 2/6 = 6/42 or 3/21 (notice the denominator changed)

Question 224

What is a sampLING distribution?

Answer 224

a pile of statistics. A pile of p-hats or x-bars.

Question 225

What is a t-crit?

Answer 225

It is the same as z crit. It is the number of sd you reach out in your CI. To find it, do INVT(area in one tail, degrees of freedom)

Question 226

In which sampling methods do all subjects have the same probability of being chosen?

Answer 226

SRS, cluster, systematic and stratified all give subjects equal likelihood of being chosen.

Question 227

What is a p-value

Answer 227

It is the probability of getting your sample randomly if the null were true. Basically, how likely is it that your sample statistic came from the Null Model.

Question 228

What are the names of four two-sample procedures we do?

Answer 228

2 proportion Z interval2 proportion Z test2 sample mean T interval2 sample mean T test

Question 229

what is a biased estimator?

Answer 229

When the sampling distribution (pile of sample stats, x bars or p hats) is NOT centered on the true population parameter. If you were weighing people and there was a 1 pound weight on the scale, the pile would be centered 1 pound higher. Baised.

Question 230

What if you want more confidence?

Answer 230

get a bigger net.. (wider conficence interval) (or increase sample size)

Question 231

Can you draw the alpha/beta/power diagram?

Answer 231

BE ABLE TO SKETCH THE ALPHA BETA POWER DIAGRAM from the original pregnancy worksheet. Know where everything is. This helps you understand how alpha, beta and power interact.

Question 232

What is wrong with using volunteers in a survey?

Answer 232

(Volunteers are often upset or emotionally attached) Those who volunteer may not be like the rest of the population. An example may be, if you’re trying to find our how often people volunteer for things. So you ask for volunteers to take the survey. A question may be “when was the last time you volunteered for something?” Well. they all just volunteered for the survey!

Question 233

What is a critical value?

Answer 233

It is the amount of standard errors you’ll reach out, depending on your confidence (a t or z). Example.. 68% crit z = 1 .. For 95% crit z = 2 (well, 1.96).. For means.. Use t crits

Question 234

What is a margin of error?

Answer 234

critical * s.d. It is how far you reach out in a confidence interval.. You reach up and down one of these, so the interval is actually 2 margins of error wide.

Question 235

What symbols do we use for population standard deviation and sample standard deviation?

Answer 235

Sigma for population and s for sample.

Question 236

What is a simple random sample?

Answer 236

put all of the names in a hat. every group is possible. pull the numbers

Question 237

How to make TREES with screening tests or tests that give you conditionals????

Answer 237

SPLIT UP POPULATION FIRST&raquo_space;»» then split the groups by outcomes of the test

Question 238

How is undercoverage different from non response

Answer 238

undercoverage you don’t even ask people, non-response you ask, but they don’t answer.

Question 239

what is a conditional distribution?

Answer 239

A distribution with a condition (within the table), along only one row or one column. What percent of the 8th graders liked bacon. The condition is 8th graders, so you are only interested in 8th graders. NOT IN THE MARGINS. You are given a condition.. Then read along that row or column.

Question 240

Suppose you sample 150 people randomly from a city to make an inference about the city, and then you sample 150 people randomly from around the country to make an inference about the entire country, which will you be more confident in????

Answer 240

It will tell you just as much about both. Same reliability (if sample is representative). Sample size determines confidence. To get more confidence you need a larger sample (not a smaller population)

Question 241

What is a control group?

Answer 241

The group that doesn’t get a treatment (or gets the old treatment). It helps us see the impact of the environment. It gets the placebo or standard care but goes through all of the motions

Question 242

What percentile is Q1?

Answer 242

25th

Question 243

What does mutually exclusive mean?

Answer 243

Same as disjoint.. Can’t both happen.

Question 244

Can numbers be CATEGORICAL?

Answer 244

sure. Zip codes, sports jersey numbers, telephone numbers, social security nunmbers, area codes these are categorical.

Question 245

How can you decrease sampling error?

Answer 245

Get a larger sample

Question 246

Will 95% of other statistics be within my interval?

Answer 246

NO!!! You have no idea where your statistic is (or your interval) in regards to true parameter

Question 247

How do you describe a scatterplot?

Answer 247

DIRECTION FORM STRENGTH and STRANGE

Question 248

If the p-value is low, (below alpha), how do you write conclusion?

Answer 248

With p-value this low (show p value < alpha) I reject the null hypothesis. There is strong evidence that the proportion of students who eat rice has changed.

Question 249

if you switch x and y does r change?

Answer 249

NO. The strength stays the same.

Question 250

when can you expect the first success? (mean of GEO)

Answer 250

1/p this tells you, on average, when the first success will occur .

Question 251

What is a continuous probability function or curve?

Answer 251

A line or curve (like the normal model) that has an area of exactly one. The probability is found by finding the area between the boundaries given.

Question 252

Does a census make sense?

Answer 252

A census is ok for small populations (like Mr. Nystrom’s students) but impossible if you want to survey “all US teens”

Question 253

Does sample size matter, or percent of population?

Answer 253

Sample size. A sample of 150 will say as much about a population of 2,000 as it will about a population of 2,000,000. The sample size determines level of confidence and interval widths..

Question 254

what is the best way to reduce bias?

Answer 254

randomness and good sampling methods.

Question 255

How do you describe distributions (histograms)?

Answer 255

Shape-Cener-Spread- and STRANGE (Outliers and gaps) some say GSOCS. where’s yo GSOCS?

Question 256

What is the sure way to assign treatments correctly?

Answer 256

throw names in hat and first half in group 1 and the rest group 2. . Or number subjects from 1-n and use randint until you get half for group 1.

Question 257

Can you make a 100% confidence interval?

Answer 257

Sure, I’m 100% confident that it will snow between 0 and 500 feet tomorrow.

Question 258

Do parameters vary?

Answer 258

NO!!! Statistics do because they are calculated from samples, different samples have different statistics. they vary from sample to sample. The parameter doesn’t vary because there is only one.

Question 259

What is the null for a 2 sample mean T?

Answer 259

mu1=mu2 OR mu1-mu2=0 there is no diff

Question 260

What is the difference between single-blind and double blind?

Answer 260

Single blinding is when all individuals in either one of the classes are blinded; double-blinded is when everyone in BOTH classes are blinded. Classes are: subjects and the other is treatment givers + evaluators

Question 261

A bag has 3 red chips and 4 blue chips.. If you grab a red one on the first try and keep it, WTPT the next one is red?

Answer 261

2 out of 6

Question 262

How do statistics from big samples compare to small? (notice this doesn’t ask about DATA)

Answer 262

Larger sample statistics have less variablility, so statistics from larger samples are closer to eachother and to the parameter. Statistics from smaller samples are more spread out, further away from true parameter.

Question 263

what is pythagorean theorem of stats? (variances add)

Answer 263

st dev of combined model is: sqrt(st dev squared + st dev squared) or more if you combine more

Question 264

What is a census?

Answer 264

Like a sample of the entire population, you get information from every member of the population

Question 265

What is cluster sampling?

Answer 265

Cluster- grab clusters of the population. Usually for convenience. GO to 20 randomly chosen schools and sample 50 students in each. each cluster should be representative ( like the population) use a few clusters.

Question 266

What is a random sample?

Answer 266

When you choose a sample by using randomness… rolling dice, choosing names from a hat, or other REAL RANDOMLY generated sample. Humans can’t really do this well without the help of a calculator, cards, dice, or slips of paper.

Question 267

If you switch x and y will slope change?

Answer 267

YES (but not just reciprocal) slope is rsy/sx , to get new slope you can use shortcut: r 2 /old slope (reciprocal times r 2 )

Question 268

How do students often mix up IQR and St. Dev

Answer 268

They INCORRECTLY think that Q1 is 1sd below the mean and Q3 is 1sd above the mean. THIS IS NOT TRUE!!! Q1 is only .67 sd above the mean and Q2 is .67 below

Question 269

What is the “nearly normal” condition for regression? (aka large enough sample)

Answer 269

Make sure the histogram of the residuals is normalish.

Question 270

Why do we plug 999 into normcdf?

Answer 270

It needs a z score, but we can’t plug in infinity. So we go down or up 999 standard deviations and that pretty much gets everything

Question 271

What does the CLT say about the distribution of actual sample data?

Answer 271

Nothing? The sample will be distributed similar to the population. Bimodal populations have bimodal samples. The CLT only talks about distributions (histograms) of sample statistics, of summaries, which are groups of means.., NOT OF INDIVIDUALS!!!! NOT DATA

Question 272

What are the two (three) types of experiments?

Answer 272

1. Completely randomized 2. Randomized block (and matched pairs which is just blocking by pairs)

Question 273

How are we using random numbers in experiments vs studies?

Answer 273

In a study, we randomly choose subjects to survey from the population as a whole. In an expermint we

Question 274

What do OGIVES look like?

Answer 274

They all start at the bottom left (0%) and go to top right (100%)

Question 275

A 4 year high school of 2000 students, sampling 40 high students: Explain how clustering has “impossible groups”

Answer 275

You couldn’t get 2 people from each classroom, because you would be randomly choosing classrooms and asking everyone in those classes.

Question 276

What is the null for a chi squared test for homogeneity?

Answer 276

The [samples of —] are similarly distributed.

Question 277

What is the difference between a completely randomized and a randomized block?

Answer 277

In a completely randomized experiment, all of the subjects names go into ONE HAT and you pick for treatment groups. In a randomized block design you have more hats (a hat for males, a hat for females etc) and pick for treatments from each.

Question 278

Why does it make sense to double-blind an experiment?

Answer 278

It reduces bias in an experiment. If subjects don’t know what treatment they’re receiving, they won’t change their habits based on that knowledge. If evaluators don’t know which treatment each subject is receiving, they won’t bias the true results based on the results they expect to see

Question 279

Diff between association or correlation?

Answer 279

association is talking about a relationship. If you see a pattern in the scatterplot, there is an association. Correlation is an actual calculated number (two quantitative variables) . NEITHER MEAN ONE CAUSES THE OTHER!!!

Question 280

How do you describe CENTER for unimodal and symetric distributions?

Answer 280

use the MEAN

Question 281

notation: what is t*

Answer 281

critical t, how many SE you are reaching up and down in a confidence interval for means

Question 282

A bag has 3 red chips and 4 blue chips.. WTPT you reach in and first grab a blue and then grab a red without replacing?

Answer 282

4/7 * 3/6 = 12/42 or 6/21

Question 283

Example of wording bias

Answer 283

Do you support food assistance and nutrition programs for children living in poverty? VS. Do you approve of supporting lazy people on welfare?

Question 284

WHat is the null for a chi squared test for independence”

Answer 284

The [two variables in context] are independent.

Question 285

can disjoint events be independent? EXPLAIN

Answer 285

NO.. If they are disjoint then knowing one tells you that the other couldn’t happen so they are always NOT INDEPENDENT

Question 286

are any populations actually normal?

Answer 286

no, nothing is normal, just normalish. The only normal thing is the model we use.

Question 287

A 4 year high school of 2000 students, sampling 40 high students: Explain how systematic has “impossible groups”

Answer 287

You couldn’t get the first 40 people alphabetically (because you are taking every nth)

Question 288

Describe the distribution of a sample vs the population

Answer 288

It will look like the population. The distribution of a sample is a histogram made from the sample, which will look kind of like the population. If the population is bimodal, then the distribution of the sample is bimodal. The SAMPLING distribution of a bunch of means, however, will look normalish.

Question 289

In the fertilizer experiment, how could you plan to eliminate the confounding variable?

Answer 289

USING RANDOMIZED BLOCK DESIGN. Make each table a block, and then randomly assign fertilzer A and B to the plants at each table. Compare the fertilizers for table 1, then compare the fertilizers on table 2.

Question 290

What is the IQR?

Answer 290

Interquartile range a measure of spread. Q3-Q1. The distance from Q1 to Q3. The regular range is Hi-Lo, this is the inner range, the interquartile range.

Question 291

If you are testing to see if a math program works in your town (that will cost 4 million to implement) describe a type 1 and type 2 error.

Answer 291

Type 1: you think it worked, but it didn’t so you spend 4 million on a program that isn’t good.Type 2: It worked, but you didn’t notice, so you miss the opportunity to adopt a good math program.

Question 292

what does geometric model tell us about

Answer 292

it is about FIRST SUCCESS What is likelihood first success is on 5th trial?

Question 293

what does “ 90% confidence” mean in a 90% interval for avg weight of mice (2.3, 3.5) in ounces

Answer 293

90% of intervals made this way would catch the true mean weight. If you took 1000 samples and made 1000 intervals, about 900 intervals would catch the true weight, 100 would not.

Question 294

What is retrospective study?

Answer 294

A retrospective study is a study that looks backwards in time (or at the present moment).

Question 295

What is area under ANY probability curve?

Answer 295

1 (or 100%)

Question 296

what is independent?

Answer 296

when P(A)=P(A|B) When the probability of A is the same even when B is also true Knowing B does not affect the probability of A. (can also be checked by P(A)*P(B)=P(AandB))

Question 297

what is a test statistic?

Answer 297

a t or z score (or chi squared) that you use to find a p value

Question 298

What is a way to think about the three conditions?

Answer 298

1. Sample is random2. Sample is small enough (<10%)3. Sample is large enough (np&nq>10 for props, n>30 for means or the histogram is normalish)EXTRAS: chi squared exp at least 5 in each cell, regression- random resid

Question 299

What is difference between subject and experimental unit?

Answer 299

Humans who are experimented on are commonly called subjects in an experiment. Subjects like dogs, days, plants and anything not human are called Experimental Units

Question 300

Why is it called the “least squares regression line?” the LSRL?

Answer 300

Because, after you find the mean-mean point, you fix the line so that it minimizes the squared vertical distancesto that line from each point. It minimizes the squared residuals, the least squares..

Question 301

what is the shortcut invnorm?

Answer 301

gives data value from percentile, skips Z score. Invnorm (percentile, mean, sd)

Question 302

Are models what really happen?

Answer 302

No. A model train is not a real train. We use models to say what kind of happens.

Question 303

give an Example of a MULTISTAGE sample

Answer 303

Suppose you want to poll urban, suburban and rural citizens, you can divide a map into those strata, and then randomly choose neighborhoods or streets in each and ask everyone on those streets. Here you stratified by community type and then clustered by street.

Question 304

Q: How can you get a parameter? A: By taking a ___________

Answer 304

Census

Question 305

When there is no relationship between two variables, we say they are

Answer 305

independent (or not associated)

Question 306

What is the null for a paired T test?

Answer 306

xbar diff=0 (the average diff is zero)

Question 307

notation: what is mu - mu

Answer 307

true difference between two populatinon means

Question 308

What is matched pair design?

Answer 308

A type of blocking where you match subjects to other “like” subjects MOST OFTEN SEEN WHEN YOU COMPARE A SUBJECT TO ITSELF!! (like pre-post tests)

Question 309

what does binomial model tell us about?

Answer 309

exactly x successes in K trials. What is likelihood of exactly 3 heads out of 13 flips?

Question 310

What do you have to look for with two sample procedures:

Answer 310

1. You have to check the conditions for each sample AND2. The samples have to be independent from eachother

Question 311

What is a “percentile?”

Answer 311

It tells you the percent of data BELOW a certain value

Question 312

If you take two bits of information from each subject there are two possible tests you could do. If the data is quantitative, you can do___ and if it is categorical, you can do a ______

Answer 312

regression t test, chi-squared test for independence.

Question 313

What is the difference between categorical VARIABLES and categorical DATA?

Answer 313

The Variable is the overall category. Like “EYE COLOR”. The data is the actual measurement from the subjects. Like “blue, brown, blue”

Question 314

How can you describe spread?

Answer 314

range, IQR, stand dev, variance, or simply say: From here, to about here

Question 315

What if a scatterplot goes straight across horizontally?

Answer 315

NO ASSOCIATION. That would be like height and IQ, they are independent so each height has about the same IQ.

Question 316

What are random variables?

Answer 316

If you randomly choose people from a list, then their hair color, height, weight and any other data collected from them can be considered random variables.

Question 317

Do we add or subtract st dev when combining models?

Answer 317

neither you always just add variances. Square the st devs, add them, then take sqrt.

Question 318

How can you tell if variables in a contingency table are independent?

Answer 318

If the distributions are the same across the variables.. Then it doesn’t DEPEND so INDEPENDENT. Ex: 30% of freshman and 30% of seniors like cabbage.

Question 319

notation: What is Ha

Answer 319

The alternative. This is what you are trying to prove.

Question 320

IF you are testing to see if a marketing program increases sales, describe a type 1 and type 2 error.

Answer 320

Type 1: you think it increased sales but it didn’gType 2: It actually increased sales but you didn’t notice

Question 321

One tail or 2 tailed? How do you tell?

Answer 321

if it just says “changed” or “different”.. Then it is 2 sided.. DOUBLE THE P VALUE!If it says “more” “less than” “greater” etc.. Then it is just one sided..

Question 322

How can you describe shape?

Answer 322

TWO THINGS: modes and symmetry.unimodal, bimodal, multimodal AND uniform, symmetric, skewed

Question 323

What is systematic sampling?

Answer 323

collecting data from every nth subject.

Question 324

What is “probability of at least one” the same as?

Answer 324

1-probability of NONE.

Question 325

What does invnorm do?

Answer 325

It gives you the Z SCORE from a percentile

Question 326

What is difference between 2 Samp T test and a PAIRED T Test

Answer 326

In a two sample T test you are comparing TWO SAMPLE AVERAGES to eachother. In a PAIRED T test you are looking just at JUST ONE average of the THIRD LIST… They are paired.. So you find each individual BEFORE-AFTER and take the average of all of those differences. You do ONE SAMPLE T TEST on it because you really have one mean. You just the average or the difference list.

Question 327

How do you match OGIVES to histograms?

Answer 327

RECTANGLE DROP!!

Question 328

how do you find z and t crit?

Answer 328

for z crit.. INVNORM(area in 1 tail) for t crit. INVT(area in 1 tail, deg freedom). area in 1 tail is just ( 1-CL) / 2

Question 329

What is response bias? How do you avoid it?

Answer 329

Response bias is any influence that may sway the respondent e.g wording of the question, interviewer’s behavior/background. Therefore, in a survey, ask questions that allow respondents to answer comfortably and honestly. Keep the wording “indifferent” or neutral in some way in order to unduly favor one response over another.

Question 330

If you have one group and ask them two questions, what type of chi squared test is it?

Answer 330

Test for independence.

Question 331

you reject when _____________ evidence

Answer 331

you reject when YOU HAVE EVIDENCE

Question 332

If you are doing a one tailed test with alpha=.05.. What confidence interval goes with that?

Answer 332

90% confidence interval tests a one tailed test. There is 5% in the tail.

Question 333

How do you find point estimate from an interval?

Answer 333

It is in the dead center of interval, so take the average of the upper and lower bounds.

Question 334

What is the missed opportunity error? (the “I didn’t notice” error)

Answer 334

Type 2

Question 335

What do you call things that are not independent?

Answer 335

associated. Or not independent. We generally don’t say DEPENDENT (unless talking about y variable on a scatterplot).

Question 336

How do you describe SPREAD for bimodal or multimodal?

Answer 336

talk about the outer edges of the clusters “from here to here” or use the IQR.

Question 337

what is the emperical rule?

Answer 337

mean 68-95-99.7 yeah!

Question 338

How do you find relative frequency?

Answer 338

just divide frequency by TOTAL?.

Question 339

not associated is the same as being ____________

Answer 339

independent

Question 340

Is it always better to do a census or to sample?

Answer 340

depends on the availablility of the data. If the you want to look at SAT vs GPA, you may easily be able to get all of the school’s data and do that study (a census). If you have to go out and get the info, you may want to take a sample to save time and energy.

Question 341

What’s wrong: Age and height have a correlation of 2.7

Answer 341

WRONG. Correlation must be between 1 and -1

Question 342

If the distribution is bimodal or multimodal, what would you use for center and spread statistics?

Answer 342

Talk about each mode (center) and maybe use the range or IQR. You could also say “one group seems to go from __ to __ and the other from about __ to __”

Question 343

Why are there different standard deviation formulas for population and sample? Arent they the same thing?

Answer 343

Both equations are actually doing the same thing. They both attempt to calculate the true population proportion. When you have all of the data from the population you just divide by n and get the actual SD. BUT If you only have a sample then you are using that to make a guess (inference) at what the population standard deviation is.. What happens is that samples tend to have less spread so their SD underestimates the population, BUT, when you divide by n-1 instead of n, It gives you a better estimate of what the population standard deviation is.

Question 344

Year in school (F,S,J,S) and Pizza Preference (pepperoni or cheese) are __________ because _______________

Answer 344

independent because all grades have similar preference distributions.. 40% cheese, 30%pepperoni, 20% veggie 10% other

Question 345

What is a null model?

Answer 345

It is a sampling distribution. It tells us how sample statistics would vary if the null were true. It is centered at the null. A pile of p-hats or x-bars.

Question 346

How can you check for “straight enough?”

Answer 346

Residuals plot fool! check the resids

Question 347

What is a standard deviation?

Answer 347

average (typical) distance to the mean (about). It is how far you expect a random value to be away from the middle.

Question 348

What is the “you think it worked but it didn’t” error?

Answer 348

Type 1

Question 349

what happens to t models as n gets larger?

Answer 349

The models look more like the normal model. An infinite sample size would give a t model identical to the normal model.

Question 350

What is the “nearly normal” condition for means? (aka large enough sample)

Answer 350

If n>30, good to go. If n<30, then you have to make sure the histogram of the sample looks normalish.

Question 351

What does a “significance level of .02” mean?

Answer 351

set alpha= .02 and reject only p-values below that

Question 352

How do you describe CENTER for skewed or distributions with outliers?

Answer 352

use the MEDIAN

Question 353

What do we sometimes call a categorical variable?

Answer 353

qualitative

Question 354

marginal distribution

Answer 354

distribution in the margins (outside of the table). The overall distributions of a single variable in contingency table.

Question 355

What is the total area under the normal curve?

Answer 355

1 or 1.000

Question 356

How do you find the mean of a random variable if it is in a table?

Answer 356

values in L1, percents in L2, run 1-VAR STATS L1, L2.

Question 357

What is the difference between confounding and lurking?

Answer 357

Confounding is in experiments, like sunlight confounding a fertilizer experiment. Lurking is when you think hot chocolate causes ski accidents. “lurking”is actually a word not even used in AP STATS.

Question 358

what is representative?

Answer 358

It means that the sample statistics will be kind of like the population parameters.. The sample “looks like” the population.

Question 359

Lurking variable: Why are there more ice cream sales on days that there are more surfing accidents? Is the ice cream putting surfers at risk?

Answer 359

The WEATHER is the lurking variable. When it is a nice day, more surfers and more ice creams are sold. So, the WEATHER causes both to go up and down together.

Question 360

How else can you explain power?

Answer 360

The likelihood you correctly reject a false null.. The likelihood you correctly detect what you were trying to detect

Question 361

How can you increase power?

Answer 361

Increase alpha or increase sample size..

Question 362

what is df for goodness of fit?

Answer 362

cells - 1

Question 363

How do you undo a log when solving? log x = stuff or log x = m

Answer 363

10^ stuff 10 stuff that will get you x or x= 10 m

Question 364

What are the xbar and mu in t-test? (on calc)

Answer 364

xbar is your sample mean, mu is your hypothesized population mean

Question 365

Computer Output: What is “S”

Answer 365

The average, or typical residual.. Standard deviation of the residuals typical distance from actual value to the model’s prediction. About how far off your prediction is likely to be.

Question 366

What is difference between non response bias and undercoverage?

Answer 366

You may ask someone to take a survey, they may say no. They may feel differently than the people who decide to take the survey. In this case, that is non-response bias. Undercoverage happens when you didn’t even ask some people to take the survey. The people you didn’t even ask might feel different.

Question 367

When there is a relationship between two variables, we say that they are

Answer 367

associated (or not independent)

Question 368

What is a level in an experiment? give example

Answer 368

Example. For the Factor “SLEEP” the, level(s) would be how many hours the subjects were alowed to sleep.. 4 hours, 6 hours, 8 hours.. 3 levels

Question 369

4 ingredients: What is “compare?”

Answer 369

Having something to compare your treatment with helps you see its effectiveness. Usually you compare to a control group (or a previous value when the subjects are their own control group).

Question 370

what is probability?

Answer 370

THE LONG RUN RELATIVE FREQUENCY!!

Question 371

Think of the minimum value, the median and the IQR, which is impacted by shifting (adding a constant?)

Answer 371

adding a value shifts the entire histogram to the right, so the min and the median will increase by that amount, BUT THE IQR WILL NOT CHANGE.

Question 372

What are the 3 steps in hypothesis testing AFTER YOU CHECK CONDITIONS?

Answer 372

1. Make your Ho and Ha 2. Make a Null Model (centered at null, use your Ho as center and in calculations, use your sample size).. This is a sampling distribution for the statistics if the null were true. 3. THINK then CHECK. use your statistic (p-hat, x-bar, phat1-phat2, xbar1-xbar2) to calculate your test statistic and then p value

Question 373

If something is correlated is it associated?

Answer 373

Yes. If it is correlated then it must be associated. However, if it is associated, it may not be correlated.

Question 374

If you take two bits of information from each subject there are two possible tests you could do. If the a chi squared test would be for _____ data and a regression t-test would be for ______ data

Answer 374

categorical, quantitative.

Question 375

4 ingredients: What is “randomization?”

Answer 375

You want to randomly assign subjects to treatment groups.

Question 376

If you want to calculate the probability (%) something falls between two values in a normal model, what do you do?

Answer 376

find z scores for both value, and then normcdf (Z LOW, Z HIGH )

Question 377

binocdf

Answer 377

(n,p,x) .. Probability of X OR LESS successes in N trials. (CUMULATIVE probability)

Question 378

What is the null model (the sampling distribution) in a 2 sample mean t-test?

Answer 378

a pile of differences of TWO MEANS samples, taken from a bunch of PAIRS of samples. Take two samples, calculate two means, subtract to get a difference, PUT THE DIFFERENCE IN THE PILE.

Question 379

What is meant by cumulative frequency?

Answer 379

ADD up the frequencies as you go. Suppose you are selling 25 pieces of candy. You sell 10 the first hour, 5 the second, 3 the third and 7 in the last hour, the cumulative frequency would be 10, 15, 18, 25

Question 380

How do you find mean and sd of probability model?

Answer 380

put values in L1, probabilities in L2, and run “1-var stats L1,L2” and you get it!

Question 381

What are the “good” sampling methods?

Answer 381

SRS (simple random sample), stratified, clustered, systematic, multistage

Question 382

What is Q2 also known as?

Answer 382

the median

Question 383

the output for normcdf(Zleft, Zright) is_______

Answer 383

the area under the normal curve between the given z scores

Question 384

How do you write conclusion if you fail to reject?

Answer 384

With a p-value this high (p-value > alpha) I fail to reject the null. There is not enough evidence to say that more students like eggs now.

Question 385

Systematic, how do you find the N for every nth subject, and then how do you proceed?

Answer 385

TOTAL POP/SAMPLE SIZE= your n (round down). Then use RAND INT to Randomly choose first. RANDINT(1, n). And then take every nTH.

Question 386

In which sampling methods do all GROUPS have the same probability of being chosen?

Answer 386

Only in SRS do all GROUPS have the same probability of being chosen, all of the other methods have IMPOSSIBLE GROUPS.

Question 387

how do you describe direction? (in regression)

Answer 387

positive or negative

Question 388

Name types of bias

Answer 388

undercoverage, non response, response, voluntary

Question 389

When drawing a graph or chart, what do you have to remember to do?

Answer 389

LABEL AXES, make a KEY(if needed ) AND GIVE IT A NAME!!! “Figure 1: Age and Food Preference”

Question 390

independent is the same as __________

Answer 390

not associated

Question 391

notation: what is phat - phat

Answer 391

difference between two sample proportions

Question 392

name 2 differences between observational studies and experiments

Answer 392

1. Experiments can prove causation (studies can’t) . 2. In experiments, you assign treatments (studies you just watch)

Question 393

notation: what is x-bar

Answer 393

mean of your sample

Question 394

What is the null model (the sampling distribution) in a 2-proporiton Z test?

Answer 394

a pile of differences of TWO PROPORTIONS, taken from a bunch of PAIRS of samples. Take two samples, calculate proportions, subtract to get a difference, PUT THE DIFFERENCE IN THE PILE.

Question 395

What if you want more cofidence with same size interval?

Answer 395

increase your sample size

Question 396

What are the differences between the subjects in strata and the subjects in clusters?

Answer 396

the “strata” are homogeneous, or have similar traits. The clusters are heterogeneous, or mixed traits.

Question 397

How are mean, median and mode positioned in a skewed left histogram?

Answer 397

goes in that order, mean median mode

Question 398

What is a categorical variable?

Answer 398

Qualitative variables are like categories: Blonde, Listens to Hip Hop, Female, yes, no? etc.

Question 399

Give an example of independent variables

Answer 399

If 80% prefer cheese and only 20% prefer pepperoni IN EACH GRADE AT BHS then they all have the same preference, so grade doesn’t matter. We say “school year and pizza choice are independent”

Question 400

how do you combine probability models?

Answer 400

add or subtract the means, and then ADD THE VARIANCES ALWAYS

Question 401

how do you find deg freedom?

Answer 401

n-1 for one sample, for 2 samples you must use calculator. For PAIRED use n-1, REGRESSION IS n-2

Question 402

what is n! ?

Answer 402

it is “n factorial” example: 5! = 54321= 120. tells you how many ways you can arrange n objects.

Question 403

What is beta?

Answer 403

It is probability that you’ll make a Type II error.. P(Type II error)

Question 404

Interpret r squared

Answer 404

r squared % of variability in y can be explained by the model with x. The rest is in residuals

Question 405

how do you describe form of a scatterplot?

Answer 405

straight or curved?

Question 406

Do you use p-hat or p-null when you calculate your standard error in a null model?

Answer 406

use p-null..

Question 407

How do you find Margin of Error from an inteval?

Answer 407

It is half the width.. (HI-LO divided by 2) Remember you stand at statistic (point estimate) and reach up and down a Margin of Error. So an inteval is always exactly 2 margins of error wide)

Question 408

Give example of a matched pair design study for fuel efficiency

Answer 408

Testing fuel efficiency of different gasolines. Subjects use both fuel A for a month and fuel B for a month and compare, based on their driving habits and vehicle, which was more efficient. BE SURE TO RANDOMLY CHOOSE WHICH ONE GOES FIRST FOR EACH SUBJECT.

Question 409

What are the mean and standard deviation of a sampling distribution for a mean?

Answer 409

mean is mu and standard deviation is sigma/root n (look at formula sheet) N(mu, sigma/rootn)

Question 410

data or datum?

Answer 410

datum is singular.. Like “hey dude, come see this datum I got from this rat!” data is the plural.. “hey look at all that data Edgar got from those chipmunks over there!!”

Question 411

What is the “hot hand” view of probability?

Answer 411

Misrepresentation of the law of large numbers. If someone flipped a coin and it landed on heads 4 times in a row you’d expect it to be heads again because “heads is hot”.. NOT TRUE..

Question 412

If asked to compare distributions, what should you write about?

Answer 412

A sentence comparing the SHAPES. A sentence comparing the CENTERS. A center comparing the SPREADS. and a sentence comparing the STRANGE STUFF. (GSOCS)

Question 413

Compare data to statistics

Answer 413

Data is each little bit of information collected from the subjects?. They are the INDIVIDUAL little things we collect? we summarize them by, for example, finding the mean of a group of data. If it is a sample, then we call that mean a “statistic” if we have data from each member of population, then that mean is called a “parameter”

Question 414

what is the LSRL

Answer 414

the “least squares regression line” that line you plot OR That equation

Question 415

How many SD wide is the IQR in a normal distribution?

Answer 415

NOT 2!!!! Think about it. The middle 68% is 2 sd wide, since the IQR is only the middlest 50% it must be less than 2. try [invnorm(.75)] x2. You find that it is only 1.35 SD wide if the distribution is nearly normal.

Question 416

A 4 year high school of 2000 students, sampling 40 high students: Describe a stratified sample

Answer 416

Stratify by year. Randomly choose 10 FR, 10 SO, 10 JU and 10 SENIORS

Question 417

What is a statistic?

Answer 417

A numerical summary of a sample. Like a mean, median, range? of a sample.

Question 418

what is a parameter?

Answer 418

some numerical summary of a population. Often called “the parameter of interest.” It is what we are often trying to find.. It doesn’t vary. It is out there and STUCK at some value, it is the truth, and you’ll probably not ever know it! We try to catch them in our confidence intervals, but sometimes we don’t (and we don’t know it!). It Could be the mean of a population, the standard deviation of a population, the proportion of successes in a population, the slope calculated from a population, a difference of 2 means from 2 population, a difference of 2 proportions from population

Question 419

What does GSOCS stand for?

Answer 419

Gaps Shape Outliers Center Spread (put on your gsocs when comparing distributions) be sure to talk about each one clearly (make a list)

Question 420

What percentile is the median (aka Q2)?

Answer 420

50th

Question 421

What is a quantitative variable?

Answer 421

Quantitative variables are numeric like: Height, age, number of cars sold, SAT score

Question 422

What is a CUMULATIVE FREQUENCY GRAPH?

Answer 422

An OGIVE. It shows the added up totals as you go left to right.

Question 423

If something is associatied is it correlated?

Answer 423

Not necessarily. It can be associated and have a zero correlation ( parabolic scatterplot) or categorical variables.

Question 424

what is the shortcut normcdf?

Answer 424

gives % from raw data, skips Z score. normcdf (low VALUE, high VALUE, mean, sd)

Question 425

If there is a screening test for mathphobia, describe a type 1 and a type 2 error

Answer 425

Type 1: You think the person has mathphobia, but they don’tType 2: They have mathphobia, but you didn’t notice

Question 426

If a distribution is skewed right, what will be greater, the mean or median? WHY?

Answer 426

Mean. The mean moves further to the right to keep balance.

Question 427

When can you round?

Answer 427

AT THE VERY END!!! (keep at least 3 digits until end!)

Question 428

how are t models like Normal models?

Answer 428

both are unimodal and symmetric. T models aren’t as high and have more area in tails, that’s why you have to reach out a little further than z for same confidence.

Question 429

Give a simple example showing that adding a constant doesn’t change the spread, but changes the center. (this always happens)

Answer 429

Data set: 1,2,3,4,5 Spread (range):4, Center: 3 add three and get new data set: 3,4,5,6,7 spread:4 Center: 5 (center went up, spread stayed the same). The IQR and SD will stay the same, but median and mean go up 3. Called shifting, or sliding the data.

Question 430

notation: what is xbar- xbar

Answer 430

difference between two sample means

Question 431

How is Blocking in an Experiment Similar to Stratifying in a Sample?

Answer 431

The two are similar because they divide the subjects into homogenous groups where the subjects are all similar (these traits were already present in the population)

Question 432

Which hypothesis shows what you are trying to prove?

Answer 432

The alternative.

Question 433

what happens if you ADD a constant to each value in a data set?

Answer 433

it is SHIFTED only. Does not impact spread. This effects all of the data values and measures of center (mean, med) and quartiles, deciles, etc, IT DOES NOT CHANGE THE SPREAD! (IQR, St Dev, Range all stay the SAME).

Question 434

How do you describe SPREAD for skewed distributions (or distributions with outliers?)

Answer 434

Use the IQR

Question 435

How do you make confidence interval for slope?

Answer 435

STAT +/- CRIT SE of slope

Question 436

where are the “outlier fences?”

Answer 436

1.5 IQR above Q3 and 1.5 IQR below Q1. Just a rule of thumb.

Question 437

What is diff between homogeneity and test for independence?

Answer 437

homogeneity is more than one sample and asking about one variable, independence is just one sample with two variables.

Question 438

How can you describe the center of a distribution?

Answer 438

OPTIONS: give the mean (balance), median (splits area in half), mode (peaks, if bimodal talk about both modes) or say “centered around ____”

Question 439

What is the purpose of matching?

Answer 439

it isolates the differences between subjects so help see the impact of the treatment.

Question 440

Make a guess as to what relative cumulative frequency is?

Answer 440

It is the ADDED up PERCENTAGES.. An example is selling candy, 25 pieces sold overall., with 10 the first hour, 5 the second, 3 the third, and 7 the fourth hour, we’d take the cumulative frequencies, 10, 15, 18 and 25 and divide by the total giving cumulative percentages. .40, .60, .64, and 1.00. Relative cumulative frequencies always end at 100 percent.

Question 441

4 ingredients: What is “replication?”

Answer 441

Having enough subjects. You don’t want to test fertilizer on just one plant.

Question 442

What is sampling variability?

Answer 442

same as sampling error. The natural variation of sample statistics.. NOT DATA.. Samples vary. so do their statistics.. Parameters do not vary!

Question 443

If r= 0.8. An x value that is 2 standard deviations above the mean will have a predicted y value that is _______

Answer 443

1.6 standard deviations above the mean in the Y direction

Question 444

using calculator: suppose 30% of dogs have fleas. WTPT more than 10 out of 40 have fleas?

Answer 444

1 - 10 or less1-binocdf(40, .30, 10)

Question 445

What is quantitative data?

Answer 445

The actual numbers gathered from each subject. 211 pounds. 67 beats per minute.

Question 446

How is a sampling frame different from the population?

Answer 446

Suppose you are wondering how elderly people on the cape feel about a new medicare law. If you go to nursing homes and randomly sample residents, then the frame is “elderly people at those nursing homes.” Your population is still elderly people on cape cod.

Question 447

How can you use random numbers to sample?

Answer 447

Number the subjects 00-99 (if less than 100) or 000-999 (if less than 1000) or 0000 to 9999 etc.. then use a random number table taking one, two, three or four numbers at a time. Throw out repeats.

Question 448

What are we confident in?

Answer 448

our confidence lies in our interval. if we took another sample.. We’d have a different interval..

Question 449

Example of nonresponse bias

Answer 449

In a survey, a person does not answer a few questions (or a person is on your list and you can’t get a hold of them)

Question 450

What is frequency?

Answer 450

How often something comes up

Question 451

How do you find df in 2 samples?

Answer 451

USE CALCULATOR.(or smaller sample-1). you have to run an interval or a test on your TI and read the output (unless you want to use the equation.)

Question 452

What is a mistake that people make with the law of large numbers?

Answer 452

they make short term predictions. The law of large numbers talks about the LOOOOOOONG run relative frequency.

Question 453

How do you find Expected Count?

Answer 453

for GOF: Exp %(total).. For indep and homog: ROW*COL/TOTAL

Question 454

What are the mean and standard deviation of a sampling distribution for a proportion?

Answer 454

mean is p and sdandard deviation is root pq/n (look at formula sheet) N(p, root (pq/n) )

Question 455

When sampling, what kind of sample are we striving to get?

Answer 455

A representative sample, we want our sample to have similar charactaristics as the population

Question 456

How do you find Q1 and Q3?

Answer 456

Q1 is the median of the bottom half and Q3 is the median of the upper half (they are the 25th and 75th percentiles)

Question 457

How do you descrive SPREAD for unimodal and symmetric distributions?

Answer 457

use the standard deviation

Question 458

what are the names of four one-sample procedures we do?

Answer 458

1 proportion Z interval1 proportion Z test1 sample mean T interval1 sample mean T test

Question 459

WHAT ARE THE TWO INDEPENDENCE EQUATIONS USED FOR CHECKING?

Answer 459

P(A)=P(A|B) or P(A)*P(B)= P(A and B)

Question 460

How many ways can I arrange M N W Z ?

Answer 460

4! 432*1 = 24 ways

Question 461

For both a chi squared test for independence and a regression t test you are looking for an association, how do the null hypotheses differ?

Answer 461

The chi squared will be in words.. Ho: the variables are not associated. The regression t test will be with symbols (and words). Ho: Beta = 0 (the slope is zero) . Saying “beta=0” is the same as saying “there is no association”

Question 462

What are the “bad” sampling methods.

Answer 462

convenience samples, voluntary samples

Question 463

When are box plots used most often?

Answer 463

When comparing a bunch of different sets of data.

Question 464

How does multiplying by a constant impact the summary statistics of a data set? (or random variable)

Answer 464

It is SCALED. Both center and spread are effected. They all (mean, median, IQR, SD, range) get multiplied by three. (BE CAREFUL, remember the variance is the SD squared, so the variance gets multiplied by 9).

Question 465

How do you describe CENTER for bimodal or multimodal?

Answer 465

talk about the modes (the lumps, the clusters)

Question 466

What is a sample?

Answer 466

A subset of a population, often taken to make inferences about the population. We calculate statistics from samples.

Question 467

Is sampling error a mistake?

Answer 467

IT IS NOT A MISTAKE!!! Because the data in samples are generally different, the statistics calculated from one sample to another vary and are generally not equal to the parameter. This variablilty of STATISTICS is called sampling error.

Question 468

not independent is the same as

Answer 468

associated

Question 469

notation: what is Ho

Answer 469

The NULL, the dull, the “things haven’t changed” hypothesis

Question 470

What is the NULL HYPOTHESIS?

Answer 470

The DULL HYPOTHESIS, the nothing changed hypothesis, the no-difference hypothesis, the “he’s telling the truth” hypothesis, the “No trickery” hypothesis

Question 471

How do you do the tricky reverse tree problems (like test says pregnant.. What is probability you actually are?)

Answer 471

SPLIT UP POPULATION FIRST&raquo_space;»» then split the groups by outcomes of the test.. BE SURE TO LABEL THE OUTCOMES and multiply the branches to the end To find P(pregnant|test says pregnant), only look at the 2 branches that end with test saying pregnant.. put the actual pregnant over the sum of both pregnant and non.

Question 472

What “designs” are there for experiments?

Answer 472

completely randomized, random block, and matched pair design(type of block)

Question 473

How is a margin of error different from a standard error?

Answer 473

A margin of error is a NUMBER OF STANDARD ERRORS. It is how far up or down you go in a confidence interval. A standard error tells you about the spread of a pile of statistics (a sampling distribution).

Question 474

How can you straighten data?

Answer 474

Do stuff to the y (square it, root it, log it, etc) and recheck the plot. Remember to put the transformation into your equation. Example Sqrt y = 4.33 - 2.03 x

Question 475

how can you decide the right test? What are the 3 questions?

Answer 475

1 or 2 samples? Proportions (z) or Means (t)? Test or Interval?(YES/NO/PROP/Z)

Question 476

how are beta and power related

Answer 476

as one increases, the other decreases, and vice versa. They have to because they BOTH ADD TO ONE!!! Power + Beta = 1

Question 477

What is the Fundemental Theorem of Statistics?

Answer 477

The CLT!! The Central Limit Theorem!

Question 478

What is meant by relative frequency?

Answer 478

The PERCENT of time something comes up (frequency/total)

Question 479

How do you undo sqrt when solving? like sqrt(x) = stuff

Answer 479

^2 (raise stuff to power of 2 to get x)

Question 480

Can you predict an X by using a Y?

Answer 480

NOT WITH THE SAME EQUATION! BE CAREFUL!! Don’t just solve for x. You have to change the entire equation and start from scratch. (run LinReg L 2 , L 1 )

Question 481

What if the scatterplot is curved?

Answer 481

Either straighten the scatter and fit a line, or keep it and fit a curve Try quadreg, cubicreg, lnreg, logreg and check the graph and the r.

Question 482

what is that (n over k) thing in the binomial equation?

Answer 482

n choose k it tells you how many ways you can choose k objects from a set of n things. The formula is n!/(n!(n-k)!) the two numbers on bottom add to the number up top. These are coefficients in expanded binomials and can also be found in Pascal’s Triangle

Question 483

What is wrong with using voluteers in an experiment?

Answer 483

Not much. In an experiment, we are not looking for a sample that is like the population. We just want to see the effectiveness of a treatment. It is fine if the subjects are all similar. In fact it is best sometimes when they are!

Question 484

Give example of randomized block design for a new anxiety med vs placebo with 100 volunteers (60m and 40f)

Answer 484

Block by gender. Randomly assign 30m to new and rest placebo. Randomly assign 20w new and rest placebo.

Question 485

What is prospective study?

Answer 485

Prospective study is when you study the experimental unit’s present and future.

Question 486

What are some strong r values and some weak r values

Answer 486

Strong r values are close to 1 or -1, like -0.83 or 0.94. Weak r values are close to zero like 0.10 or -0.06

Question 487

geopdf

Answer 487

(p,x) probability of FIRST SUCCESS being ON the Xth trial

Question 488

Why don’t we always use the mean, we’ve been calculating it all of our life ?

Answer 488

It is not RESILIENT, it is impacted by skewness and outliers

Question 489

Interpret residual: Points below the line/negative resid

Answer 489

“the model overpredicted” or “Actual value was below the the expected (or predicted)”

Question 490

What is the difference between discrete and continuous variables?

Answer 490

Discrete can be counted, like “number of cars sold” they are generally integers (you wouldn’t sell 9.3 cars), while continuous would be something like weight of a mouse? 4.344 oz.

Question 491

What is a weakness of a SRS?

Answer 491

Suppose you want a sample of 50 high school students, with an SRS, although unlikely you could get “all freshmen” which wouldn’t be representative.

Question 492

If the mean is above the median, the distribution may be

Answer 492

skewed right. the mean follows the tail

Question 493

What is an unbiased estimator?

Answer 493

When the sampling distribution (pile of sample stats) is centered on the true population parameter. Basically, the pile of x bars should be around mu.

Question 494

What is the difference between a population mean and a sample mean?

Answer 494

population mean is the mean of a population, it is a parameter, sample mean is a mean of a sample, so it is a statistic. We use sample statistics to make inferences about population parameters.

Question 495

4 ingredients: What is “BLOCKING?”

Answer 495

If you think different groups of subjects may respond differently to treatments because of location, gender, age, then you make BLOCKS, and make sure to compare the treatments within each block.

Question 496

First step in interpreting slope

Answer 496

Write “slope units y over 1 unit x” and look at it.

Question 497

can independent events be disjoint? EXPLAIN

Answer 497

NO, if they are independent, then knowing one doesn’t change the probability of the other, but if they are disjoint, knowing one makes the other impossible, so it does change the probability to 0

Question 498

What is the difference between the distribution of a sample and a sampling distribution?

Answer 498

A distribution of a sample is just a histogram of the DATA in a sample. A sampling distribution is made from an bunch of sample STATISTICS. It is the distribution of the statistic that was calculated from those many many samples.

Question 499

Give an example of matched pair design for comparing a new blood pressure medication to an older version?

Answer 499

Have subjects use the new medication for a month and the old one for a month and compare. Be sure to randomize which month and blind.

Question 500

What is wording bias

Answer 500

A type of response bias, When the wording of the question impacts response to it. (type of response bias)