DECK 11 BEFORE INFERENCE MIXED

Question 1

<p>Compare population to sample</p>

Answer 1

<p>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.</p>

Question 2

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

Answer 2

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

Question 3

<p>How can you check for "straight enough?"</p>

Answer 3

<p>Residuals plot fool!</p>

<p>check the resids</p>

Question 4

<p>What are random variables?</p>

Answer 4

<p>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.</p>

Question 5

How to find P(at least 1)?

Answer 5

1-P(none)

Question 6

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

Answer 6

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

Question 7

<p>What percentile is Q1?</p>

Answer 7

<p>25th</p>

Question 8

<p>How do you find outliers in regression?</p>

Answer 8

<p>they don'tfollow the "flow"</p>

<p>(pinky trick, cover with you pinky.. Then uncover.. Does it follow the flow?)</p>

Question 9

<p>What do you call things that are not independent?</p>

Answer 9

<p>associated. Or not independent. We generally don't say DEPENDENT (unless talking about y variable on a scatterplot).</p>

Question 10

<p>What point is on every regression line?</p>

Answer 10

<p>the mean-mean point. (x bar, y bar).</p>

<p>This point is generally not one of the points on the scatterplot.</p>

<p>Usually none of the scatterplot points are on the regression line.</p>

Question 11

<p>is r sensitive to outliers?</p>

Answer 11

<p>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.</p>

Question 12

<p>Interpret residual: Points above the line/positive resid</p>

Answer 12

<p>"the model underpredicted" or "actual performance was above the expected performance</p>

Question 13

give an Example of a MULTISTAGE sample

Answer 13

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 14

<p>Q: How can you get a parameter? A: By taking a \_\_\_\_\_\_\_\_\_\_\_</p>

Answer 14

<p>Census</p>

Question 15

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

Answer 15

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 16

<p>Does a high r value mean anything?</p>

<p>(can it look strong, but not be?)</p>

Answer 16

<p>Sure. It can. It tells you strength of LINEAR relationship.</p>

<p>BUT</p>

<p>CHECK THE SCATTER. One outlier or typo can make it look STRONG.</p>

Question 17

<p>How do you describe CENTER for bimodal or multimodal?</p>

Answer 17

<p>talk about the modes (the lumps, the clusters)</p>

Question 18

<p>What is a sample?</p>

Answer 18

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

Question 19

<p>How is r calculated?</p>

Answer 19

<p>r = sum(Z_xZ_y) / (n-1)</p>

<p>it is the sum of rectangle areas on the standardizes Zaxes</p>

Question 20

<p>Why do we plug 999 into normcdf?</p>

Answer 20

<p>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</p>

Question 21

Why do you have to Stratify?

Answer 21

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 22

what is independent?

Answer 22

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 23

<p>Interpret r squared</p>

Answer 23

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

Question 24

<p>What is meant by relative frequency?</p>

Answer 24

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

Question 25

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

Answer 25

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

Question 26

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

Answer 26

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 27

Why is it called the "least squares regression line?" 

the LSRL?

Answer 27

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

It minimizes the squared residuals, the least squares....

Question 28

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

Answer 28

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

Question 29

are there any normal samples?

Answer 29

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

Question 30

What is the difference between a sample and a census?

Answer 30

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 31

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

Answer 31

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 32

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

Answer 32

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 33

Interpret residual: Points below the line/negative resid

Answer 33

"the model overpredicted"

or

"Actual value was below the the expected (or predicted)"

Question 34

What is area under ANY probability curve?

Answer 34

1 (or 100%)

Question 35

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

Answer 35

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 36

Compare Descriptive and Inferential STATS

Answer 36

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

Question 37

How can you use random numbers to sample?

Answer 37

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 38

How do you interpret slope EQUATION?

rSy/Sx

Answer 38

for each increase of 1 st dev in x direction,

you go r st dev in y direction.

2st dev in x, you go 2r st. dev in y.

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

Question 39

What is homoscedasticity?

Answer 39

equal scatter along the regression line

Question 40

Compare data to statistics

Answer 40

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 41

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

Answer 41

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

Question 42

What is response bias? How do you avoid it?

Answer 42

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 43

Do we add or subtract st dev when combining models?

Answer 43

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

Question 44

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 44

a datum, or a data value.

Question 45

If something is correlated is it associated?

Answer 45

Yes.

If it is correlated then it must be associated.

However, if it is associated, it may not be correlated.

Question 46

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

Answer 46

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 47

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

Answer 47

binocdf (20, .30, 7)

Question 48

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

Answer 48

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

Question 49

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

Answer 49

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 50

What is the expected value?

Answer 50

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

Question 51

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

Answer 51

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

Question 52

What's up with extrapolation? Is it OK?

Answer 52

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

Question 53

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

Answer 53

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 54

What is difference between non response bias and undercoverage?

Answer 54

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 55

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

Answer 55

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

Question 56

How do you find mean and sd of probability model?

Answer 56

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

Question 57

First step in interpreting slope

Answer 57

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

Question 58

binocdf

Answer 58

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

Question 59

How do you match OGIVES to histograms?

Answer 59

RECTANGLE DROP!!

Question 60

what does geometric model tell us about

Answer 60

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

Question 61

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 61

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

Question 62

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

Answer 62

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

Question 63

What does normcdf do?

Answer 63

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

Question 64

How is undercoverage different from non response

Answer 64

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

Question 65

what is the shortcut invnorm?

Answer 65

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

Question 66

how do you describe form of a scatterplot?

Answer 66

straight or curved?

Question 67

How do you undo squares or cubes?

like if you have x²= stuff 

or x³= stuff

Answer 67

^ 1/2 or ^ 1/3

(raise stuff to these powers to get x)

Question 68

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

Answer 68

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 69

Does a census make sense?

Answer 69

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

Question 70

What is a level in an experiment? give example

Answer 70

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 71

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

Answer 71

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

Question 72

What percent of the data is above Q3?

Answer 72

25%

Question 73

Example of undercoverage

Answer 73

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

Question 74

What is difference between completely randomized and random block design?

Answer 74

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 75

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

Answer 75

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

Question 76

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

Answer 76

geocdf (.30, 5)

Question 77

What is a "percentile?"

Answer 77

It tells you the percent of data BELOW a certain value

Question 78

What is probability first success is on 7th try?

Answer 78

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

Question 79

What percentile is the median (aka Q2)?

Answer 79

50th

Question 80

What do we sometimes call a categorical variable?

Answer 80

qualitative

Question 81

Does the regression line (LSRL) go through a lot of points?

Answer 81

No, usually it goes through NONE!

It just goes through the center of the cloud of points.

Question 82

What is Statistics?

Answer 82

The study of variability

Question 83

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

Answer 83

when np and nq are over 10

Question 84

what is leverage?

Answer 84

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 85

How can you match boxplots to histograms?

Answer 85

USE THE FISH TANK METHOD!

Question 86

What is a Z score?

Answer 86

The number of standard deviaiton away from the mean

Question 87

What's the difference between stratified and cluster sampling?

Answer 87

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

Question 88

Why is it called "binomial"

Answer 88

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

Question 89

How to make TREES with screening tests????

Answer 89

SPLIT UP POPULATION FIRST >>>>>> then split the groups by outcomes of the test

Question 90

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

Answer 90

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 91

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

Answer 91

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

Question 92

What is BIAS in sampling?

Answer 92

A systematic FLAW in your method.

Question 93

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 93

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 94

How are we proving causation in experiments and obs studies?

Answer 94

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

Question 95

How are we using random numbers in experiments vs studies?

Answer 95

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

Question 96

How do you find Q1 and Q3?

Answer 96

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 97

the output for normcdf(Zleft, Zright) is_______

Answer 97

the area under the normal curve between the given z scores

Question 98

what is representative?

Answer 98

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

Question 99

How do you descrive SPREAD for unimodal and symmetric distributions?

Answer 99

use the standard deviation

Question 100

what is a complement?

Answer 100

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

Question 101

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

Answer 101

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

Question 102

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

Answer 102

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

Question 103

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

Answer 103

7-Apr

Question 104

how do you combine probability models?

Answer 104

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

Question 105

Why randomize in an experiment?

Answer 105

To reduce confounding variables (and bias).

Question 106

What is a continuous probability function or curve?

Answer 106

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 107

What percent of the data is below the median?

Answer 107

50%

Question 108

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

Answer 108

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

Question 109

What are the "good" sampling methods?

Answer 109

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

Question 110

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

Answer 110

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

Question 111

What is a weakness of a SRS?

Answer 111

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

Question 112

What is the "hot hand" view of probability?

Answer 112

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 113

4 ingredients: What is "replication?"

Answer 113

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

Question 114

What is the total area under the normal curve?

Answer 114

1 or 1.000

Question 115

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

Answer 115

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

Question 116

if you switch x and y does r change?

Answer 116

NO. The strength stays the same.

Question 117

What is the difference between quantitative and categorical data?

Answer 117

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 118

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

Answer 118

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 119

What does invnorm do?

Answer 119

It gives you the Z SCORE from a percentile

Question 120

which calculator function gives you a percent?

Answer 120

normcdf(Z left, Z right)

Question 121

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

Answer 121

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

Question 122

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

Answer 122

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 123

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 123

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

Question 124

How do you undo an ln (natural log) when solving?

ex:   ln x = stuff

or:  ln x = m

Answer 124

e^stuff

or

e^m

Question 125

Does the IQR capture 68% of the data?

Answer 125

NO. it catches the middle 50%.

Question 126

How can you describe spread?

Answer 126

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

Question 127

What is a random sample?

Answer 127

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 128

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

Answer 128

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

Question 129

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

Answer 129

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

Question 130

What are DESCRIPTIVE STATS?

Answer 130

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

Question 131

What is the main purpose of a placebo ?

Answer 131

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 132

What percent of the data is above Q3?

Answer 132

25%

Question 133

How is a sampling frame different from the population?

Answer 133

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 134

What is a population?

Answer 134

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 135

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

Answer 135

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 136

What is a factor? give example

Answer 136

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

Question 137

what is disjoint?

Answer 137

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

Question 138

What percentile is Q3?

Answer 138

75th

Question 139

What are 2 branches of AP STATS?

Answer 139

Inferential and Descriptive

Question 140

How do you get equation from computer output?

variable            coeff           indep: doc

constant           0.005

genet              - 0.233

Answer 140

doc = 0.005 - 0.233 (genet)

Question 141

what is probability?

Answer 141

THE LONG RUN RELATIVE FREQUENCY!!

Question 142

Give example of factors and levels

Answer 142

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

Question 143

What is the problem with convenience sampling?

Answer 143

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 144

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

Answer 144

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

Question 145

What are the two types of observational studies?

Answer 145

Retrospective, and Prospective

Question 146

How many ways can I arrange M N W Z ?

Answer 146

4! 4*3*2*1 = 24 ways

Question 147

How do you describe distributions (histograms)?

Answer 147

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

Question 148

What is a sampling frame?

Answer 148

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

Question 149

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

Answer 149

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

Question 150

Computer ouput:

What does "constant" mean?

Answer 150

It is the y intercept

Question 151

How can you describe the center of a distribution?

Answer 151

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

Question 152

How are voluntary and convenience samples similar…

Answer 152

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 153

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

Answer 153

use the MEDIAN

Question 154

How do you undo and exponent?

Example

stuff^x= other

a^x=b

Answer 154

log other / log stuff

that gives you x

or 

x = (log b) / (log a)

 

Question 155

What is the purpose of matching?

Answer 155

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

Question 156

What is the law of averages?

Answer 156

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 157

What is a control group?

Answer 157

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 158

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

Answer 158

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 159

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

Answer 159

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

Question 160

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

Answer 160

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

Question 161

What is the line that you plot?

Answer 161

IT IS A MODEL!

It is the LSRL and it is the model we are talking about

Question 162

What are the percentiles for Q1, med, and Q3?

Answer 162

25, 50 and 75

Question 163

Another name for "skewed right" is

Answer 163

positively skewed

Question 164

Can numbers be CATEGORICAL?

Answer 164

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

Question 165

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

Answer 165

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 166

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

Answer 166

Mu for population mean, xbar for sample mean.

Question 167

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 167

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

Question 168

What is stratified sampling?

Answer 168

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

Question 169

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

Answer 169

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

Question 170

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

Answer 170

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 

or you can plot L2 vs RESID

Question 171

4 ingredients: What is "compare?"

Answer 171

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

Question 172

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

Answer 172

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 173

How do you find the median from an OGIVE?

Answer 173

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

Question 174

What is the mode?

Answer 174

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

Question 175

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

Answer 175

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

Question 176

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

Answer 176

goes in that order, mean median mode

Question 177

What is Q2 also known as?

Answer 177

the median

Question 178

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

Answer 178

Sigma for population and s for sample.

Question 179

what is the best way to reduce bias?

Answer 179

randomness and good sampling methods.

Question 180

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

Answer 180

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 181

When can you round?

Answer 181

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

Question 182

independent is the same as __________

Answer 182

not associated

Question 183

What is the mode?

Answer 183

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

Question 184

What is wording bias

Answer 184

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

Question 185

Things that cause nonresponse bias ?

Answer 185

(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 186

Can there be a correlation between grade and music preference?

Answer 186

No, music preference is categorical.

There is an association, however.

Question 187

What if a scatterplot goes straight across horizontally?

Answer 187

NO ASSOCIATION.

That would be like height and IQ, they are independent so each height has about the same IQ.

Question 188

What is wrong with using volunteers in a survey?

Answer 188

(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 189

What is the difference between response bias and nonresponse bias?

Answer 189

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 190

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

Answer 190

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

Question 191

What percent of the data is between Q1 and Q3?

Answer 191

the middle 50%. That is the IQR

Question 192

What is a frequency distribution?

Answer 192

A table, or a chart, that shows how often certain values or categories occur in a data set.

Question 193

what does influential mean?

Answer 193

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 194

Can you eliminate sampling error?

Answer 194

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

Question 195

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

Answer 195

Median (center) and IQR (spread)

Question 196

What is the difference between quantitative and categorical variables?

Answer 196

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

Question 197

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

Answer 197

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 198

What is sampling error?

Answer 198

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

Question 199

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

Answer 199

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 200

Example of wording bias

Answer 200

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

Question 201

where are the "outlier fences?"

Answer 201

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

Question 202

describe a scatterplot's strength?

Answer 202

give the r value (if straight),

or say…

"tightly packed… loosely packed"

Question 203

How can you straighten data?

Answer 203

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

Question 204

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

Answer 204

2.5, 16, 50, 84, 97.5

Question 205

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

Answer 205

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

Question 206

Which calculator function gives you a z score?

Answer 206

invnorm(%ile)

Question 207

not associated is the same as being ____________

Answer 207

independent

Question 208

What is wrong with using voluteers in an experiment?

Answer 208

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

Question 209

How do you describe CENTER for unimodal and symetric distributions?

Answer 209

use the MEAN

Question 210

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

Answer 210

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

Question 211

What if the scatterplot is curved?

Answer 211

Either straighten the scatter and fit a line,

or keep it and fit a curve

Try quadreg, cubicreg, lnreg, logreg and check the graph and the r.

Question 212

How do you undo sqrt when solving?

like

sqrt(x) = stuff

Answer 212

^2

(raise stuff to power of 2 to get x)

Question 213

How do we use representative samples in experiments and studies?

Answer 213

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

Question 214

How is BIAS different from SAMLING error

Answer 214

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

Question 215

How do you describe SPREAD for bimodal or multimodal?

Answer 215

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

Question 216

What is "probability of at least one" the same as?

Answer 216

1-probability of NONE.

Question 217

can independent events be disjoint? EXPLAIN

Answer 217

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

Question 218

How can you decrease sampling error?

Answer 218

Get a larger sample

Question 219

What does GSOCS stand for?

Answer 219

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

Question 220

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

Answer 220

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

Question 221

geopdf

Answer 221

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

Question 222

How are statistics and parameters different?

Answer 222

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 223

What is the sure way to assign treatments correctly?

Answer 223

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 224

What is a residual?

Answer 224

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 225

How do you undo a log when solving?

log x = stuff

or

log x = m

Answer 225

10^ stuff

10^stuff

that will get you x

or

x= 10^m

Question 226

What values can r be?

Answer 226

from -1 to +1

(r near 0 is WEAK)

Question 227

How do you interpret slope?

Answer 227

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 228

are any populations actually normal?

Answer 228

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

Question 229

What is a contingency table?

Answer 229

shows distributions across 2 variables like gender and music pref. AKA 2-way table

Question 230

How do you find a certain percentile on an OGIVE?

Answer 230

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 231

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

Answer 231

(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 232

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

Answer 232

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

Question 233

what is a conditional distribution?

Answer 233

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 234

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

Answer 234

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

Question 235

When are box plots used most often?

Answer 235

When comparing a bunch of different sets of data.

Question 236

What is systematic sampling?

Answer 236

collecting data from every nth subject.

Question 237

What is the difference between categorical VARIABLES and categorical DATA?

Answer 237

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

Question 238

WHAT ARE THE TWO INDEPENDENCE EQUATIONS USED FOR CHECKING?

Answer 238

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

Question 239

What is categorical data?

Answer 239

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

Question 240

What is a categorical variable?

Answer 240

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

Question 241

How are we making inferences differently in experiments vs studies?

Answer 241

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

Question 242

What is prospective study?

Answer 242

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

Question 243

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

Answer 243

independent (or not associated)

Question 244

What "designs" are there for experiments?

Answer 244

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

Question 245

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

Answer 245

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 246

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

Answer 246

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

Question 247

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

Answer 247

skewed right... the mean follows the tail

Question 248

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

Answer 248

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 249

What is frequency?

Answer 249

How often something comes up

Question 250

What are the two (three) types of experiments?

Answer 250

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

Question 251

Can you predict an X by using a Y?

Answer 251

NOT WITH THE SAME EQUATION!

BE CAREFUL!!  Don't just solve for x...

You have to change the entire equation and start from scratch.

(run LinReg L₂, L₁)

Question 252

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

Answer 252

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

Question 253

What do we look for in a residuals plot?

Answer 253

To proceed, it should look random.

if there is a pattern, then find a new model or proceed with caution.

Question 254

Example of response bias

Answer 254

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 255

What is the difference between confounding and lurking?

Answer 255

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 256

Does r² tell direction?

Answer 256

NO

 r² is always positive, so you can't use it to see if the relationship is negative.

Question 257

Give a quick example of associated variables

Answer 257

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 258

Does sample size matter, or percent of population?

Answer 258

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 259

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 259

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 260

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

Answer 260

undercoverage

Question 261

does correlation mean causation?

Answer 261

NO WAY DUDE

Question 262

What is "mutually exclusive?"

Answer 262

disjoint. Can't happen at the same time.

Question 263

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

Answer 263

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 264

what is pythagorean theorem of stats?

Answer 264

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

Question 265

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

Answer 265

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 266

What is meant by cumulative frequency?

Answer 266

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 267

Computer Output:

What is "S"

Answer 267

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 268

What is quantitative data?

Answer 268

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

Question 269

How can you describe shape?

Answer 269

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

Question 270

What is a simple random sample?

Answer 270

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

Question 271

what is the law of large numbers?

Answer 271

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 272

Association and Independence. How are they related?

Answer 272

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 273

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 273

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

Question 274

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

Answer 274

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 275

What other regressions does your calculator do?

Answer 275

Quadreg, cubicreg, lnreg, etc.

just be careful when substituting while writing the equation given.

Question 276

what is a linear model?

Answer 276

It is an equation you can use or a line of a graph,

but it is just a model that says what kind of happens,

and can be used to ESTIMATE WHAT MIGHT HAPPEN

Question 277

What are the "bad" sampling methods.

Answer 277

convenience samples, voluntary samples

Question 278

What do OGIVES look like?

Answer 278

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

Question 279

associated is the same as __________

Answer 279

not independent

Question 280

What is retrospective study?

Answer 280

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

Question 281

When we say the average teenager are we talking about mean

Answer 281

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 282

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

Answer 282

p for population and p-hat for sample

Question 283

what is the LSRL

Answer 283

the "least squares regression line"

that line you plot

OR 

That equation

Question 284

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

Answer 284

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 285

What is the IQR?

Answer 285

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 286

What does SHIFT and SCALE mean?

Answer 286

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

Question 287

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 287

weight loss (pounds)

Question 288

what is a probability model?

Answer 288

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

Question 289

What is the variance?

Answer 289

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 290

what is b₁ and b_o ?

Answer 290

b₁ is the SLOPE,

b_o is the intercept.

Question 291

What is the five number summary?

Answer 291

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

Question 292

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

Answer 292

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

Question 293

geocdf

Answer 293

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

Question 294

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 294

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

Question 295

How do you get equation from computer output?

variable            coeff           indep: age

constant           7.2

Height              3.5

Answer 295

For this case:

age = 7.2 + 3.5 (height)

Question 296

what does binomial model tell us about?

Answer 296

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

Question 297

Is sampling error a mistake?

Answer 297

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

Question 298

4 ingredients: What is "randomization?"

Answer 298

You want to randomly assign subjects to treatment groups.

Question 299

Does high r squared mean a good model?

Answer 299

CHECK SCATTER FIRST..

Make sure model "FITS" the data.

You should check your scatterplot and residuals plot to make sure model is appropriate and no outliers present… then it means something

So YES, but after you check the resids.

Question 300

What is a standard deviation?

Answer 300

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

Question 301

What is a probability distribution?

Answer 301

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

Question 302

data or datum?

Answer 302

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 303

Compare data to parameters

Answer 303

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 304

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 304

only 1.4 S.D above the mean for weight.

(for each SD in the x direction you change r SD in the y direction)

Question 305

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

Answer 305

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

Question 306

4 ingredients: What is "BLOCKING?"

Answer 306

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

Question 307

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

Answer 307

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 308

Gender and Video Game playing are___________ because_______

Answer 308

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

Question 309

what is the shortcut normcdf?

Answer 309

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

Question 310

How can the WORDING of the question lead to response bias

Answer 310

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 311

If r= 0.8.

 An x value that is 2 standard deviations above the mean will have a predicted y value that is _______

Answer 311

1.6 standard deviations above the mean in the Y direction

Question 312

What percent of the data is between Q1 and Q3?

Answer 312

50%

Question 313

How do you describe a scatterplot?

Answer 313

DIRECTION

FORM

STRENGTH

and STRANGE

Question 314

How do students often mix up IQR and St. Dev

Answer 314

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 315

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

Answer 315

Use the IQR

Question 316

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

Answer 316

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 317

What is the "mean of a random variable?"

Answer 317

The expected value… sum of probs times values

Question 318

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

Answer 318

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

Question 319

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

Answer 319

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

Question 320

If something is associatied is it correlated?

Answer 320

Not necessarily.

It can be associated and have a zero correlation

( parabolic scatterplot)

or categorical variables.

Question 321

binopdf

Answer 321

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

Question 322

What is variability?

Answer 322

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

Question 323

Compare DATA-STATISTIC-PARAMETER using quantitative example

Answer 323

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 324

name 2 differences between observational studies and experiments

Answer 324

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

Question 325

What is difference between subject and experimental unit?

Answer 325

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 326

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

Answer 326

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 327

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

Answer 327

You couldn't get all freshmen in your sample

Question 328

What is undercoverage?

Answer 328

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

Question 329

What are some strong r values and some weak r values

Answer 329

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

Question 330

What does r² tell us?

(r-squared)

Answer 330

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

Question 331

What is extrapolation?

Answer 331

Making predictions outside of the x values you have.

Question 332

4 ingredients: What is "control?"

Answer 332

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 333

how do you describe direction?

Answer 333

positive or negative

Question 334

What are INFERENTIAL STATS?

Answer 334

Look at your data, and use that to say stuff about the BIG PICTURE? like tasting soup? a little sample can tell you a lot about the big pot of soup (the population)

Question 335

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

Answer 335

WRONG.

Correlation must be between 1 and -1

Question 336

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

Answer 336

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

Question 337

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 337

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 338

How do you find 5 number summary from OGIVE?

Answer 338

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 339

not independent is the same as

Answer 339

associated

Question 340

What is the difference between discrete and continuous variables?

Answer 340

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

Question 341

What is cluster sampling?

Answer 341

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

Question 342

What is random sampling?

Answer 342

When we use chance to select a sample, like rolling dice, a random number generator, or a random number table in our selection process. We use randomization in all of the "GOOD" sampling methods.

Question 343

What is a census?

Answer 343

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

Question 344

How can you turn OGIVES into histograms?

Answer 344

RECTANGLE DROP! (bin drop)

Question 345

What percent of the data is below Q2?

Answer 345

50%

Question 346

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 346

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 347

What does r tell us?

Answer 347

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

Question 348

What is the difference between a bar chart and a histogram

Answer 348

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

Question 349

What is a CUMULATIVE FREQUENCY GRAPH?

Answer 349

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

Question 350

Will larger samples reduce BIAS?

Answer 350

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 351

What is a representative sample?

Answer 351

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

Question 352

Give example of a matched pair design study for fuel efficiency

Answer 352

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 353

Which is explanatory variable?

Answer 353

the x

the horizontal axis.

it "explains" what happens to y

Question 354

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

Answer 354

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

Question 355

What is the median?

Answer 355

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

Question 356

What do observational studies and experiments have in common?

Answer 356

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

Question 357

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

Answer 357

associated (or not independent)

Question 358

can disjoint events be independent? EXPLAIN

Answer 358

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

Question 359

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

Answer 359

binopdf(12, .30, 5)

Question 360

Give an example of independent variables

Answer 360

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 361

what is n! ?

Answer 361

it is "n factorial" example: 5! = 5*4*3*2*1= 120. tells you how many ways you can arrange n objects.

Question 362

what is the emperical rule?

Answer 362

mean 68-95-99.7 yeah!

Question 363

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

Answer 363

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 364

Name types of bias

Answer 364

undercoverage, non response, response, voluntary

Question 365

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

Answer 365

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

Question 366

Example of nonresponse bias

Answer 366

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 367

What is the difference between a parameter and a statistic?

Answer 367

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 368

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

Answer 368

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

Question 369

Give example of confounding variable.

Answer 369

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 370

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

Answer 370

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 371

Give example of incorrectly using the word "correlation"

Answer 371

"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 372

Compare DATA-STATISTIC-PARAMETER using categorical example

Answer 372

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 373

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

Answer 373

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

Question 374

What is statistically significant?

Answer 374

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 375

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 375

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 376

Diff between association or correlation?

Answer 376

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 377

How do you find relative frequency?

Answer 377

just divide frequency by TOTAL?.

Question 378

What is the placebo effect?

Answer 378

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

Question 379

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

Answer 379

Mu for population mean, xbar for sample mean.

Question 380

What is a statistic?

Answer 380

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

Question 381

When do we often use mode?

Answer 381

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 382

What does mutually exclusive mean?

Answer 382

Same as disjoint.. Can't both happen.

Question 383

Make a guess as to what relative cumulative frequency is?

Answer 383

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 384

4 INGREDIENTS TO EXPERIMENTS

Answer 384

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

Question 385

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 385

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

Question 386

how do you interpret y intercept?

Answer 386

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

Question 387

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 387

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

Question 388

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

Answer 388

Mean (center) and Standard Deviation (spread)

Question 389

which is response?

Answer 389

y variable,

the Vertical axis..

It "responds" to the x

Question 390

An unbiased sampling method will eliminate error

Answer 390

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

Question 391

Who can be blinded? ( two groups)

Answer 391

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

Question 392

What is the mean?

Answer 392

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

Question 393

will residual plots always show outliers?

(will outliers always have large residuals?)

Answer 393

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

Question 394

What is data?

Answer 394

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 395

marginal distribution

Answer 395

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

Question 396

What should we look for in resid plot?

Answer 396

Curve or pattern.

Also, it should have equalish scatter from left to right

It should look RANDOM

Question 397

What is matched pair design?

Answer 397

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 398

Can you stratify in an experiment?

Answer 398

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

Question 399

What is a parameter?

Answer 399

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

Question 400

What is a multistage sample?

Answer 400

A sample that combines several sampling methods

Question 401

If you switch x and y will slope change?

Answer 401

YES (but not just reciprocal)

slope is rsy/sx ,

to get new slope you can use shortcut:

r²/old slope

(reciprocal times r²)

Question 402

What is a quantitative variable?

Answer 402

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

Question 403

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

Answer 403

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

Question 404

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 404

6-Feb