ALL VOCAB - Open Office

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

what is b 1 and b o ?

Answer 18

b 1 is the SLOPE, b o is the intercept.

Question 19

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

Answer 19

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

Question 20

Gender and Video Game playing are___________ because_______

Answer 20

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

Question 21

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

Answer 21

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 22

Can you prove a null hypothesis true?

Answer 22

NO.. We just fail to reject it.

Question 23

How to find P(at least 1)?

Answer 23

1-P(none)

Question 24

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

Answer 24

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

Question 25

When can we use a NORMAL model to approx a binomial?

Answer 25

when np and nq are over 10

Question 26

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

Answer 26

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 27

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

Answer 27

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

Question 28

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

Answer 28

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 29

who invented the t model?

Answer 29

Bill Gosset, guiness brewing company.

Question 30

What is undercoverage?

Answer 30

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

Question 31

what is disjoint?

Answer 31

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

Question 32

What values can r be?

Answer 32

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

Question 33

What is the placebo effect?

Answer 33

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

Question 34

What does Central Limit Theorem Say?

Answer 34

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 35

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

Answer 35

A pile of means from a bunch of samples.

Question 36

Can you stratify in an experiment?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What does r tell us?

Answer 38

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

Question 39

What are 2 branches of AP STATS?

Answer 39

Inferential and Descriptive

Question 40

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

Answer 40

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

Question 41

How are we proving causation in experiments and obs studies?

Answer 41

No causation in a study, maybe association or correlation. ONLY IN EXPERIMENTS TO YOU TALK ABOUT CAUSALITY.

Question 42

What is BIAS in sampling?

Answer 42

A systematic FLAW in your method.

Question 43

Which is explanatory variable?

Answer 43

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

Question 44

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

Answer 44

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 45

What is the problem with convenience sampling?

Answer 45

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 46

what is a complement?

Answer 46

the probability that it doesn’t happen. 1-P(it happens). (together they add to 100%) (P and Q are complements)

Question 47

What is the mode?

Answer 47

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

Question 48

Give example of factors and levels

Answer 48

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

Question 49

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

Answer 49

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

Question 50

What is the five number summary?

Answer 50

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

Question 51

What percent of the data is between Q1 and Q3?

Answer 51

50.00%

Question 52

How can the WORDING of the question lead to response bias

Answer 52

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 53

What is stratified sampling?

Answer 53

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

Question 54

Compare population to sample

Answer 54

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 55

Think of the minimum value, the median and the IQR, which is

Answer 55

If you multiply a data set by a number, then the min, median and the IQR will multiply by that number.

Question 56

What is the difference between quantitative and categorical variables?

Answer 56

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

Question 57

What is a probability distribution?

Answer 57

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

Question 58

How is r calculated?

Answer 58

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

Question 59

What is a representative sample?

Answer 59

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

Question 60

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 60

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

Question 61

What is the null for a chi squared GOF test?

Answer 61

The distribution fits [the expected distribution]

Question 62

Why randomize in an experiment?

Answer 62

To reduce confounding variables (and bias).

Question 63

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

Answer 63

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 64

what does influential mean?

Answer 64

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 65

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

Answer 65

undercoverage

Question 66

We are curious about the average wait time at a Dunkin Donuts drive through in your neighborhood. You randomly sample cars one afternoon and find the average wait time is 3.2 minutes. What i

Answer 66

The parameter is the true average wait time at that Dunkin Donuts. This is a number you don’t have and will never know. The statistic is “3.2 minutes.” It is the average of the data you collected. The parameter of interest is the same thing as the population parameter. In this case, it is the true average wait time of all cars. The data is the wait time of each individual car, so that would be like “3.8 min, 2.2 min, .8 min, 3 min”. You take that data and find the average, that average is called a “statistic,” and you use that to make an inference about the true parameter.

Question 67

What is the standard sampling method? (the gold standard)

Answer 67

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 68

What is the mean?

Answer 68

the old average we used to calculate. It is the balancing point of the histogram

Question 69

Example of response bias

Answer 69

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 70

What should we look for in resid plot?

Answer 70

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

Question 71

Can there be a correlation between grade and music preference?

Answer 71

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

Question 72

What is a population?

Answer 72

the group you’re interested in. Sometimes it?s big, like “all teenagers in the US” other times it is small, like “all AP Stats students in my school”

Question 73

Compare data to parameters

Answer 73

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 74

What does normcdf do?

Answer 74

It gives you the area under the normal curve between any two z scores

Question 75

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

Answer 75

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

Question 76

What is extrapolation?

Answer 76

Making predictions outside of the x values you have.

Question 77

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

Answer 77

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

Question 78

What is a confidence interval?

Answer 78

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 79

4 INGREDIENTS TO EXPERIMENTS

Answer 79

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

Question 80

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

Answer 80

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 81

How is BIAS different from SAMLING error

Answer 81

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

Question 82

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

Answer 82

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

Question 83

notation: what is p

Answer 83

true population proportion (percent in the population)

Question 84

describe a scatterplot’s strength?

Answer 84

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

Question 85

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

Answer 85

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

Question 86

In order to reject a null hypothesis, you need ___________

Answer 86

evidence

Question 87

What are the three chi-squared models?

Answer 87

goodness of fit, test for homogeneity, test for independence

Question 88

Can you decrease alpha while increasing power (even though they move together?)..

Answer 88

Yes.. increase samle size. They move together with constant sample size.

Question 89

What are the two types of observational studies?

Answer 89

Retrospective, and Prospective

Question 90

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

Answer 90

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 91

What percentile is Q3?

Answer 91

75th

Question 92

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 92

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 93

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

Answer 93

p for population and p-hat for sample

Question 94

What is the main purpose of a placebo ?

Answer 94

To blind the subject that is being experimented on to avoid influence to the given variable therefore altering the response variable . When people think they’re getting help, they often improve anyway..

Question 95

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

Answer 95

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

Question 96

With regression computer output, how is the t-ratio and the p-value calculated?

Answer 96

T ratio is just SLOPE/ST ERROR and the p value is just TCDF(T ratio, 9999, n-2)

Question 97

What is sampling error?

Answer 97

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

Question 98

Does high r squared mean a good model?

Answer 98

CHECK SCATTER ÿFIRST.. 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 99

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

Answer 99

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

Question 100

notation: what is mu

Answer 100

true population mean (average)

Question 101

you fail to reject when ____________ evidence

Answer 101

you fail to reject when you DON’T HAVE EVIDENCE

Question 102

What is a standard error?

Answer 102

The typical, or expected, error. 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 103

What is the general formula for ALL CONFIDENCE INTERVALS?

Answer 103

STAT +/- CRIT SE

Question 104

What is probability first success is on 7th try?

Answer 104

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

Question 105

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 105

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

Question 106

what is another name for alpha level?

Answer 106

a significance level

Question 107

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

Answer 107

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

Question 108

What’s up with extrapolation? Is it OK?

Answer 108

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

Question 109

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 109

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

Question 110

geocdf

Answer 110

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

Question 111

What is a Z score?

Answer 111

The number of standard deviaiton away from the mean

Question 112

What is the median?

Answer 112

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

Question 113

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

Answer 113

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 114

Association and Independence. How are they related?

Answer 114

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 115

Compare DATA-STATISTIC-PARAMETER using quantitative example

Answer 115

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 116

what is leverage?

Answer 116

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 117

how do you interpret y intercept?

Answer 117

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

Question 118

What is the difference between a sample and a census?

Answer 118

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 119

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

Answer 119

binopdf(12, .30, 5)

Question 120

What is a point estimate?

Answer 120

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

Question 121

What is the line that you plot?

Answer 121

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

Question 122

How are statistics and parameters different?

Answer 122

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 123

How do you find a certain percentile on an OGIVE?

Answer 123

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 124

does correlation mean causation?

Answer 124

NO WAY DUDE

Question 125

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

Answer 125

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

Question 126

How are voluntary and convenience samples similar

Answer 126

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 127

How can you match boxplots to histograms?

Answer 127

USE THE FISH TANK METHOD!

Question 128

What is sampling error?

Answer 128

How far your statistic is from the parameter (how far your calculation from your sample was from the population parameter)

Question 129

Which calculator function gives you a z score?

Answer 129

invnorm(%ile)

Question 130

What is a factor? give example

Answer 130

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

Question 131

How are we making inferences differently in experiments vs studies?

Answer 131

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

Question 132

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

Answer 132

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

Question 133

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

Answer 133

Goodness of fit test.

Question 134

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

Answer 134

binocdf (20, .30, 7)

Question 135

What percent of the data is above Q3?

Answer 135

25.00%

Question 136

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

Answer 136

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 137

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

Answer 137

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 138

What is the law of averages?

Answer 138

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 139

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

Answer 139

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

Question 140

What is statistical inference?

Answer 140

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

Question 141

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

Answer 141

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

Question 142

What percent of the data is between Q1 and Q3?

Answer 142

the middle 50%. That is the IQR

Question 143

What is a residual?

Answer 143

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 144

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

Answer 144

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 145

What is alpha?

Answer 145

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 146

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 146

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

Question 147

notation: what is p-hat

Answer 147

sample proportion (percent in our sample)

Question 148

What is a parameter?

Answer 148

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

Question 149

4 ingredients: What is “control?”

Answer 149

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 150

What is the difference between response bias and nonresponse bias?

Answer 150

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 151

What is difference between completely randomized and random block design?

Answer 151

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 152

What percent of the data is below the median?

Answer 152

50.00%

Question 153

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

Answer 153

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 154

What is the difference between a bar chart and a histogram

Answer 154

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

Question 155

What is categorical data?

Answer 155

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

Question 156

What is the difference between quantitative and categorical data?

Answer 156

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 157

is r sensitive to outliers?

Answer 157

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 158

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

Answer 158

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

Question 159

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

Answer 159

You couldn’t get all freshmen in your sample

Question 160

What point is on every regression line?

Answer 160

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 161

What is the “mean of a random variable?”

Answer 161

The expected value sum of probs times values

Question 162

What’s the difference between stratified and cluster sampling?

Answer 162

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

Question 163

How do you interpret slope?

Answer 163

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 164

Why do you have to Stratify?

Answer 164

You don’t have to.. But you might want to if you feel that a simple random sample might not be representative of the population . You want your sample to be like the population. a representative sample (it represents the population well).

Question 165

when do you need crits?

Answer 165

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

Question 166

What is the mode?

Answer 166

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

Question 167

What is “statistically significant?”

Answer 167

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 168

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

Answer 168

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 169

Who can be blinded? ( two groups)

Answer 169

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

Question 170

what is a probability model?

Answer 170

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

Question 171

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

Answer 171

find z score for value, and then normcdf (-999, Zright)

Question 172

What is the variance?

Answer 172

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 173

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

Answer 173

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

Question 174

Does r 2 tell direction?

Answer 174

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

Question 175

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

Answer 175

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 176

Does the IQR capture 68% of the data?

Answer 176

NO. it catches the middle 50%.

Question 177

Compare Descriptive and Inferential STATS

Answer 177

Descriptive tells you ÿabout the data that you have, inference uses that data you have to try to say something about an entire population?.

Question 178

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 178

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

Question 179

When do you know it is GOF test?

Answer 179

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

Question 180

Another name for “skewed right” is

Answer 180

positively skewed

Question 181

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

Answer 181

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 182

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

Answer 182

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

Question 183

are there any normal samples?

Answer 183

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

Question 184

which calculator function gives you a percent?

Answer 184

normcdf(Z left, Z right)

Question 185

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 185

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

Question 186

sample size calcs FOR PROP AND MEANS

Answer 186

n= (z^2 * p * q )/ (ME ^2) and n = ( t*s / ME) ^ 2 (start with Z then do T)

Question 187

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

Answer 187

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

Question 188

What is data?

Answer 188

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 189

Computer ouput: What does “constant” mean?

Answer 189

It is the y intercept

Question 190

Can you eliminate sampling error?

Answer 190

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

Question 191

What are DESCRIPTIVE STATS?

Answer 191

Tell me what you got! Describe to me the data that you collected, use pictures or summaries like mean, median, range, etc?

Question 192

What is the other conditions for regression inference?

Answer 192

Random residuals (equal random scatter, no pattern).

Question 193

Give example of incorrectly using the word “correlation”

Answer 193

“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 194

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

Answer 194

(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 195

How can you turn OGIVES into histograms?

Answer 195

RECTANGLE DROP! (bin drop)

Question 196

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

Answer 196

Mu for population mean, xbar for sample mean.

Question 197

If there is a crazy outlier, what can you do?

Answer 197

Run the analysis with and without the outlier and write about both.

Question 198

How do you find outliers in regression?

Answer 198

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

Question 199

notation: what is p - p

Answer 199

true difference between two population proportions (percents).

Question 200

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 200

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

Question 201

when is data “paired”

Answer 201

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

Question 202

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

Answer 202

geocdf (.30, 5)

Question 203

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

Answer 203

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.

Question 204

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

Answer 204

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

Question 205

what is df for chi squared homogeneity or independence?

Answer 205

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

Question 206

What is the expected value?

Answer 206

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

Question 207

Compare DATA-STATISTIC-PARAMETER using categorical example

Answer 207

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 208

What is statistically significant?

Answer 208

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 209

what is the law of large numbers?

Answer 209

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 210

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

Answer 210

e stuff or e m

Question 211

An unbiased sampling method will eliminate error

Answer 211

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

Question 212

What is Statistics?

Answer 212

The study of variability

Question 213

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 213

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 214

What is variability?

Answer 214

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

Question 215

How do you write conclusion if you reject?

Answer 215

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 216

Example of undercoverage

Answer 216

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

Question 217

binopdf

Answer 217

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

Question 218

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

Answer 218

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 219

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 219

a datum, or a data value.

Question 220

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

Answer 220

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

Question 221

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

Answer 221

Median (center) and IQR (spread)

Question 222

How do we use representative samples in experiments and studies?

Answer 222

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

Question 223

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

Answer 223

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

Question 224

How do you ÿinterpret slope EQUATION? rSy/Sx

Answer 224

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 ÿin y. 3st dev in x, you go 3r st. dev in y.

Question 225

How is a confidence interval made?

Answer 225

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 226

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

Answer 226

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 227

Give a quick example of associated variables

Answer 227

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 228

notation: what is z*

Answer 228

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

Question 229

What is the null for a 2 prop Z?

Answer 229

p1=p2 OR… p1-p2=0, there is no diff

Question 230

What percent of the data is above Q3?

Answer 230

25.00%

Question 231

What is homoscedasticity?

Answer 231

equal scatter along the regression line

Question 232

What is the difference between a parameter and a statistic?

Answer 232

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 233

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

Answer 233

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 234

Interpret residual: Points above the line/positive resid

Answer 234

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

Question 235

What is the differnce between standard error and standard deviation?

Answer 235

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 236

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

Answer 236

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

Question 237

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

Answer 237

Mu for population mean, xbar for sample mean.

Question 238

How do you find percentiles and make a boxplot from OGIVE?

Answer 238

Go across till you hit the curve and then STRAIGHT DOWN!

Question 239

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

Answer 239

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

Question 240

When we say the average teenager are we talking about mean

Answer 240

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 241

How are power and alpha related?

Answer 241

they go up and down together

Question 242

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

Answer 242

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

Question 243

What is a sampLING distribution?

Answer 243

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

Question 244

What is a t-crit?

Answer 244

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 245

<p>How do you undo and exponent? </p>

<p>Example </p>

<p>stuff x = other </p>

<p>a x =b </p>

Answer 245

<p>log other / log stuff </p>

<p>that gives you x </p>

<p>or ÿ </p>

<p>x = (log b) / (log a) </p>

<p> ÿ </p>

Question 246

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

Answer 246

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

Question 247

A bag has 3 red chips and 4blue chips.. WTPT you grab a blue?

Answer 247

7-Apr

Question 248

What is a p-value

Answer 248

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 249

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

Answer 249

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

Question 250

what is a biased estimator?

Answer 250

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 251

What if you want more confidence?

Answer 251

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

Question 252

Can you draw the alpha/beta/power diagram?

Answer 252

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 253

What is wrong with using volunteers in a survey?

Answer 253

(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 254

What is a critical value?

Answer 254

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 255

What is a margin of error?

Answer 255

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 256

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

Answer 256

Sigma for population and s for sample.

Question 257

What is a simple random sample?

Answer 257

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

Question 258

If the distribution is unimodal and symmetric, what would you use for center and spread statistics?

Answer 258

Mean (center) and Standard Deviation (spread)

Question 259

How to make TREES with screening tests????

Answer 259

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

Question 260

How is undercoverage different from non response

Answer 260

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

Question 261

what is a conditional distribution?

Answer 261

A distribution with a condition (within the table), along only one row or one column NOT IN THE MARGINS. You are given a condition.. Then read along that row or column.

Question 262

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 262

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 263

What is a control group?

Answer 263

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 264

What percentile is Q1?

Answer 264

25th

Question 265

What does mutually exclusive mean?

Answer 265

Same as disjoint.. Can’t both happen.

Question 266

Can numbers be CATEGORICAL?

Answer 266

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

Question 267

How can you decrease sampling error?

Answer 267

Get a larger sample

Question 268

Will 95% of other statistics be within my interval?

Answer 268

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

Question 269

How do you describe a scatterplot?

Answer 269

DIRECTION FORM STRENGTH and STRANGE

Question 270

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

Answer 270

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 271

if you switch x and y does r change?

Answer 271

NO. The strength stays the same.

Question 272

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

Answer 272

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

Question 273

What is a continuous probability function or curve?

Answer 273

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 274

Does a census make sense?

Answer 274

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

Question 275

Does sample size matter, or percent of population?

Answer 275

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 276

what is the best way to reduce bias?

Answer 276

randomness and good sampling methods.

Question 277

How do you describe distributions (histograms)?

Answer 277

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

Question 278

What is the sure way to assign treatments correctly?

Answer 278

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 279

Can you make a 100% confidence interval?

Answer 279

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

Question 280

Do parameters vary?

Answer 280

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 281

What is the null for a 2 sample mean T?

Answer 281

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

Question 282

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

Answer 282

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 283

What is alpha?

Answer 283

It is the rejection area. Generally, we use .05. The significance level.

Question 284

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 284

2 out of 6

Question 285

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

Answer 285

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 286

what is pythagorean theorem of stats?

Answer 286

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

Question 287

What is a census?

Answer 287

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

Question 288

will residual plots always show outliers? (will outliers always have large residuals?)

Answer 288

Not necessarily. Some points have so much leverage, they pull the line up to it

Question 289

What is cluster sampling?

Answer 289

Cluster- grab clusters of the population. each cluster should be representative ( like the population) use a few clusters.

Question 290

What is a random sample?

Answer 290

When you choose a sample by 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 291

If you switch x and y will slope change?

Answer 291

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 292

How do students often mix up IQR and St. Dev

Answer 292

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 293

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

Answer 293

Make sure the histogram of the residuals is normalish.

Question 294

Why do we plug 999 into normcdf?

Answer 294

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 295

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

Answer 295

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 296

What are the two (three) types of experiments?

Answer 296

1. Completely randomized 2. Randomized block (matched pairs)

Question 297

How are we using random numbers in experiments vs studies?

Answer 297

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

Question 298

What do we compare our p value to in a hypothesis test?

Answer 298

compare it to alpha. if p value

Question 299

What do OGIVES look like?

Answer 299

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

Question 300

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

Answer 300

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

Question 301

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

Answer 301

The [samples of —] are similarly distributed.

Question 302

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

Answer 302

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 303

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

Answer 303

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 304

How do you make a residuals plot? (find RESID?)

Answer 304

stat>plot make a scatterplot, but instead of L1 vs L2, change L2 by putting cursor on it and going to 2nd>lists down to RESID. You can plot L1 vs RESID ÿ or you can plot L2 vs RESID

Question 305

Diff between association or correlation?

Answer 305

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)

Question 306

How do you describe CENTER for unimodal and symetric distributions?

Answer 306

use the MEAN

Question 307

notation: what is t*

Answer 307

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

Question 308

A bag has 3 red chips and 4 blue chips.. WTPT you reach in and first grab a blue and then grab a red?

Answer 308

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

Question 309

Example of wording bias

Answer 309

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

Question 310

Think of the minimum value, the mean and the standard deviat

Answer 310

If you multiply a data set by a number, then the min, mean and the SD will multiply by that number.

Question 311

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

Answer 311

The [two variables in context] are independent.

Question 312

can disjoint events be independent? EXPLAIN

Answer 312

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

Question 313

are any populations actually normal?

Answer 313

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

Question 314

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

Answer 314

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

Question 315

Describe the distribution of a sample

Answer 315

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 316

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

Answer 316

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 317

What is the IQR?

Answer 317

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 318

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 318

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 319

what does geometric model tell us about

Answer 319

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

Question 320

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

Answer 320

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 321

What is retrospective study?

Answer 321

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

Question 322

What is area under ANY probability curve?

Answer 322

1 (or 100%)

Question 323

what is independent?

Answer 323

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 324

what is a test statistic?

Answer 324

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

Question 325

What is a way to think about the three conditions?

Answer 325

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 326

What is difference between subject and experimental unit?

Answer 326

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 327

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

Answer 327

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 ÿminimizes the squared residuals, the least squares….

Question 328

what is the shortcut invnorm?

Answer 328

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

Question 329

Are models what really happen?

Answer 329

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

Question 330

give an Example of a MULTISTAGE sample

Answer 330

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 331

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

Answer 331

Census

Question 332

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

Answer 332

independent (or not associated)

Question 333

What is the null for a paired T test?

Answer 333

xbar diff=0 (the average diff is zero)

Question 334

notation: what is mu - mu

Answer 334

true difference between two populatinon means

Question 335

What is matched pair design?

Answer 335

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 336

what does binomial model tell us about?

Answer 336

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

Question 337

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

Answer 337

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

Question 338

What is a “percentile?”

Answer 338

It tells you the percent of data BELOW a certain value

Question 339

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 339

regression t test, chi-squared test for independence.

Question 340

What is the difference between categorical VARIABLES and categorical DATA?

Answer 340

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

Question 341

How can you describe spread?

Answer 341

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

Question 342

What if a scatterplot goes straight across horizontally?

Answer 342

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

Question 343

What are random variables?

Answer 343

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 344

Do we add or subtract st dev when combining models?

Answer 344

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

Question 345

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

Answer 345

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 346

notation: What is Ha

Answer 346

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

Question 347

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

Answer 347

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

Question 348

One tail or 2 tailed? How do you tell?

Answer 348

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 349

How can you describe shape?

Answer 349

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

Question 350

What is systematic sampling?

Answer 350

collecting data from every nth subject.

Question 351

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

Answer 351

1-probability of NONE.

Question 352

What does invnorm do?

Answer 352

It gives you the Z SCORE from a percentile

Question 353

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

Answer 353

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 LISTƒ?? 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 354

How do you match OGIVES to histograms?

Answer 354

RECTANGLE DROP!!

Question 355

how do you find z and t crit?

Answer 355

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 356

Suppose you want to see the relationship between gender and candy preference in squirrels. How may you do a stratified vs cluster sample

Answer 356

STRATIFIED: You can split the list of all of the squirrels in your neihborhood by gender and randomly select 20 males from th list of all of the males, and then 20 females (strata) from all of the females. CLUSTER: you can randomly choose to 5 different trees and survey all of the squirrels in those trees, assuming that there are 4 squirrels living in each tree (clusters, the trees have both M and F).

Question 357

What is response bias? How do you avoid it?

Answer 357

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 358

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

Answer 358

Test for independence.

Question 359

you reject when _____________ evidence

Answer 359

you reject when YOU HAVE EVIDENCE

Question 360

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

Answer 360

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

Question 361

How do you find point estimate from an interval?

Answer 361

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

Question 362

Why is it called “binomial”

Answer 362

These numbers come from the coefficients of expanded binomials.. (x+y)^1, (x+y)^2, (x+y)^3 .

Question 363

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

Answer 363

Type 2

Question 364

What do you call things that are not independent?

Answer 364

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

Question 365

How do you describe SPREAD for bimodal or multimodal?

Answer 365

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

Question 366

what is the emperical rule?

Answer 366

mean 68-95-99.7 yeah!

Question 367

How do you find relative frequency?

Answer 367

just divide frequency by TOTAL?.

Question 368

not associated is the same as being ____________

Answer 368

independent

Question 369

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

Answer 369

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 370

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

Answer 370

WRONG. Correlation must be ÿbetween 1 and -1

Question 371

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

Answer 371

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 372

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

Answer 372

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 373

what is a statistic

Answer 373

some numerical summary of a sample.. Could be the mean of a sample, the standard deviation of a sample, the proportion of successes in a sample, the slope calculated from a sample, a difference of 2 means from 2 samples, a difference of 2 proportions from 2 samples, a difference of 2 slopes from 2 samples.. you can make sampling distributions for any of these, and they will all be centered around the parameter…

Question 374

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

Answer 374

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

Question 375

What is a sampling frame?

Answer 375

It is the frame from which you get your sample. For instance, if you call people the frame would be “people with phones”

Question 376

What is a null model?

Answer 376

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 377

What other regressions does your calculator do?

Answer 377

Quadreg, cubicreg, lnreg, etc. just be careful when substituting while writing the equation given.

Question 378

How can you check for “straight enough?”

Answer 378

Residuals plot fool! check the resids

Question 379

What is a standard deviation?

Answer 379

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

Question 380

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

Answer 380

Type 1

Question 381

what happens to t models as n gets larger?

Answer 381

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

Question 382

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

Answer 382

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

Question 383

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

Answer 383

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

Question 384

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

Answer 384

use the MEDIAN

Question 385

What do we sometimes call a categorical variable?

Answer 385

qualitative

Question 386

marginal distribution

Answer 386

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

Question 387

What is the total area under the normal curve?

Answer 387

1 or 1.000

Question 388

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

Answer 388

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

Question 389

What is the difference between confounding and lurking?

Answer 389

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 390

what is representative?

Answer 390

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

Question 391

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 391

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 392

How do you get equation from computer output? variable ÿ ÿ ÿ ÿ ÿ ÿ coeff ÿ ÿ ÿ ÿ ÿ ÿindep: doc constant ÿ ÿ ÿ ÿ ÿ ÿ0.005 genet ÿ ÿ ÿ ÿ ÿ ÿ ÿ - 0.233

Answer 392

<p>doc = 0.005 - 0.233 (genet) </p>

Question 393

How else can you explain power?

Answer 393

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

Question 394

How can you increase power?

Answer 394

Increase alpha or increase sample size..

Question 395

what is df for goodness of fit?

Answer 395

cells - 1

Question 396

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

Answer 396

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

Question 397

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

Answer 397

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

Question 398

Computer Output: What is “S”

Answer 398

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 399

What is difference between non response bias and undercoverage?

Answer 399

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 400

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

Answer 400

associated (or not independent)

Question 401

What is a level in an experiment? give example

Answer 401

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 402

4 ingredients: What is “compare?”

Answer 402

Having something to compare your treatment with helps you see its effectiveness.

Question 403

what is probability?

Answer 403

THE LONG RUN RELATIVE FREQUENCY!!

Question 404

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

Answer 404

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 405

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

Answer 405

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 406

If something is correlated is it associated?

Answer 406

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

Question 407

associated is the same as __________

Answer 407

not independent

Question 408

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 408

categorical, quantitative.

Question 409

4 ingredients: What is “randomization?”

Answer 409

You want to randomly assign subjects to treatment groups.

Question 410

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

Answer 410

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

Question 411

binocdf

Answer 411

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

Question 412

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

Answer 412

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 413

What is meant by cumulative frequency?

Answer 413

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 414

How do you find mean and sd of probability model?

Answer 414

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

Question 415

What are the “good” sampling methods?

Answer 415

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

Question 416

What is Q2 also known as?

Answer 416

the median

Question 417

How wide is a confidence interval? (how many ME?)

Answer 417

It is 2 margins of error wide ALWAYS (DON’T CONFUSE WITH NUMBER OF SE)

Question 418

the output for normcdf(Zleft, Zright) is_______

Answer 418

the area under the normal curve between the given z scores

Question 419

How do you write conclusion if you fail to reject?

Answer 419

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 420

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

Answer 420

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 421

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

Answer 421

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

Question 422

how do you describe direction?

Answer 422

positive or negative

Question 423

Name types of bias

Answer 423

undercoverage, non response, response, voluntary

Question 424

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

Answer 424

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

Question 425

independent is the same as __________

Answer 425

not associated

Question 426

notation: what is phat - phat

Answer 426

difference between two sample proportions

Question 427

name 2 differences between observational studies and experiments

Answer 427

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

Question 428

notation: what is x-bar

Answer 428

mean of your sample

Question 429

What does SHIFT and SCALE mean?

Answer 429

Shift is when you add or subtract, scale is when you multiply

Question 430

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

Answer 430

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 431

What if you want more cofidence with same size interval?

Answer 431

increase your sample size

Question 432

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

Answer 432

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

Question 433

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

Answer 433

goes in that order, mean median mode

Question 434

What is a categorical variable?

Answer 434

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

Question 435

Give an example of independent variables

Answer 435

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 436

how do you combine probability models?

Answer 436

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

Question 437

how do you find deg freedom?

Answer 437

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

Question 438

What percent of the data is below Q2?

Answer 438

50.00%

Question 439

what is n! ?

Answer 439

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

Question 440

What is beta?

Answer 440

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

Question 441

Interpret r squared

Answer 441

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

Question 442

how do you describe form of a scatterplot?

Answer 442

straight or ÿcurved?

Question 443

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

Answer 443

use p-null..

Question 444

How do you find Margin of Error from an inteval?

Answer 444

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 445

Give example of a matched pair design study for fuel efficiency

Answer 445

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 446

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

Answer 446

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

Question 447

data or datum?

Answer 447

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 448

What is the “hot hand” view of probability?

Answer 448

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 449

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

Answer 449

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

Question 450

Compare data to statistics

Answer 450

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 451

what is the LSRL

Answer 451

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

Question 452

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

Answer 452

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 453

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

Answer 453

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

Question 454

What is a statistic?

Answer 454

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

Question 455

what is a parameter?

Answer 455

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 456

What does GSOCS stand for?

Answer 456

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

Question 457

What percentile is the median (aka Q2)?

Answer 457

50th

Question 458

When do we often use mode?

Answer 458

With categorical variables. For instance, to describe the average teenagers preference, we often speak of what ?most? students chose, which is the mode. It is also tells the number of bumps in a histogram for quantitative data (unimodal, bimodal, etc?).

Question 459

How can you decrease alpha and beta at the same time?

Answer 459

increase sample size. this will also increase power.

Question 460

What is a quantitative variable?

Answer 460

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

Question 461

What is a CUMULATIVE FREQUENCY GRAPH?

Answer 461

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

Question 462

If something is associatied is it correlated?

Answer 462

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

Question 463

what is the shortcut normcdf?

Answer 463

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

Question 464

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

Answer 464

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

Question 465

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

Answer 465

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

Question 466

When can you round?

Answer 466

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

Question 467

how are t models like Normal models?

Answer 467

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

Question 468

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

Answer 468

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 469

notation: what is xbar- xbar

Answer 469

difference between two sample means

Question 470

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

Answer 470

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 471

Which hypothesis shows what you are trying to prove?

Answer 471

The alternative.

Question 472

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

Answer 472

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 473

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

Answer 473

Use the IQR

Question 474

How do you make confidence interval for slope?

Answer 474

STAT +/- CRIT SE of slope

Question 475

where are the “outlier fences?”

Answer 475

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

Question 476

What is diff between homogeneity and test for independence?

Answer 476

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

Question 477

What do we look for in a residuals plot?

Answer 477

To proceed, it should look random. if there is a pattern, then find a new model or proceed with caution.

Question 478

How can you describe the center of a distribution?

Answer 478

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

Question 479

What is the purpose of matching?

Answer 479

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

Question 480

Make a guess as to what relative cumulative frequency is?

Answer 480

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 481

4 ingredients: What is “replication?”

Answer 481

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

Question 482

What is sampling variability?

Answer 482

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

Question 483

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

Answer 483

1.6 standard deviations above the mean in the Y direction

Question 484

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

Answer 484

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

Question 485

What is quantitative data?

Answer 485

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

Question 486

How is a sampling frame different from the population?

Answer 486

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 487

How can you use random numbers to sample?

Answer 487

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 488

What are we confident in?

Answer 488

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

Question 489

Example of nonresponse bias

Answer 489

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 490

What is frequency?

Answer 490

How often something comes up

Question 491

How do you find df in 2 samples?

Answer 491

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 492

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

Answer 492

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

Question 493

How do you find Expected Count?

Answer 493

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

Question 494

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

Answer 494

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

Question 495

How can you tell if it is a T or a Z procedure?

Answer 495

YES-NO-PROP-Z. Remember t for means, z for proportions. Think of the subjects. Could you get the info in a yes/no fashion? if so, then z-props. Do you need to get a number from each subject? if so, then t-means.

Question 496

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

Answer 496

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

Question 497

Things that cause nonresponse bias ?

Answer 497

(remember non response is that the people you ask, or try to ask don’t respond) Lazy researcher, shy survey takers, who is the questioner, environment,

Question 498

How do you find Q1 and Q3?

Answer 498

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 499

How do you descrive SPREAD for unimodal and symmetric distributions?

Answer 499

use the standard deviation

Question 500

If we use a NORMAL model to approx a BINOMIAL.. What are mean and SD?

Answer 500

mean= np and sd= root(npq). So N (np, root(npq))