MIXED VOCAB FOR WINTER

Question 1

Minimum sample size for means?

Answer 1

If population is normalish, then there is no minimum sample size. If it is skewed or bimodal or any other non-normal distribution, then n>30.

Question 2

What is a sampling distribution?

Answer 2

A pile of statistics taken from many many many samples

Question 3

What are the the sample size requirements for inference for both means and proportions?

Answer 3

1. [BOTH]You need a random sample. 2. [BOTH] Less than 10% of population 3. [DIFFER] PROPS: np>10 and nq>10, and MEANS n>30 unless from normal population, then no minimum.

Question 4

What is formula for nCr ?

Answer 4

n! / r! (n-r) !

Question 5

Describe independence and association with categorical examples.

Answer 5

Grade and pizzsa preference are independent, gender and gaming status are associated

Question 6

How do you describe an association between two quantitative variables? (scatter plot)

Answer 6

DIRECTION (pos/neg) FORM (linear,curved) STRENGTH (strong, moderate, report “r” value)

Question 7

Describe independence and association with quantitative examples.

Answer 7

Height and IQ are independent. Height and weight are associated.

Question 8

function to find a percentile in normal model?

Answer 8

INVNORM

Question 9

What is a p-value?

Answer 9

The likelihood you obtained your statistic or one more extreme due to just chance if the Null was actually true.

Question 10

What is probability?

Answer 10

Long run relative frequency. (the long run percent)

Question 11

Minimum sample size for proportions?

Answer 11

You need at lease 10 successes, np>10, and 10 failures, nq > 10

Question 12

Interpret r^2 ?

Answer 12

The percent of variablility in Y explained by the model with X

Question 13

What is error?

Answer 13

Distance from a statistic to the parameter. How far off your stat is from the truth.

Question 14

What is a Z score?

Answer 14

the number of SD a data value is away from the mean

Question 15

What graphs for CATEGORICAL data?

Answer 15

segmented bar, bar, pie, mosaic

Question 16

What does SD of residuals tell us?

Answer 16

Typical residual. Average distance to the model. About how far off we expect model to be.

Question 17

What is variance?

Answer 17

A measure of spread- the average squared distance to the mean. SD^2

Question 18

What points are outliers in regression?

Answer 18

Those that don’t follow the flow.

Question 19

function to find area under normal curve?

Answer 19

normcdf

Question 20

How do you describe the distribution of a single data set? (a histogram)?

Answer 20

SHAPE (#modes, skewness), CENTER (measure of center), SPREAD (measure of spread), STRANGE (outliers or gaps)

Question 21

Interpret SLOPE EQUATION: rSy/Sx

Answer 21

For every 1 unit of x, there is a change of SLOPE units of y

Question 22

Diff between standard deviation and standard error?

Answer 22

Standard deviation is typical distance to mean for a data point, Standard error is typical distance to parameter for a statistic in a sampling distribution.

Question 23

What is the Law of Large Numbers?

Answer 23

In the long run, after many many trials, the % of successes approaches the true probability. Think: if you flip a coin twice, you may get 0% heads, 50% heads or 100% heads. If you flip 10,000 times, you probably will have about 50% heads (def not 0 or 100)

Question 24

Suppose p value = 0.003. How would you interpret?

Answer 24

With a p-value this low (0.003 < 0.05), I reject the Ho, there is enough evidence to say [Ha in context]

Question 25

What are the measures of spread we use?

Answer 25

standard deviation, variance, range, interquartile range, standard error

Question 26

What points have influence in regression?

Answer 26

Those that would change the slope if removed (they are outliers that have leverage)

Question 27

What is margin of error?

Answer 27

Distance you reach up and down when making CI. It is CRIT * SE

Question 28

What is alpha?

Answer 28

It is the rejection threshold. Reject Ho when p-value is below alpha.

Question 29

What points have leverage in regression?

Answer 29

Those far to the left and right from x-bar

Question 30

Interpret y-intercept?

Answer 30

When X=0, the model predicts this much Y.

Question 31

What graphs for QUANTITATIVE data?

Answer 31

histogram, box/whisker, stemplot, dot plot, ogive, time plot, line graph

Question 32

What are the measures of center we use?

Answer 32

mean, median, mode

Question 33

What is a confidence interval?

Answer 33

A parameter catcher. It tries to catch the truth.

Question 34

What does “95% confident” mean?

Answer 34

If you took 100 samples and made 100 confidence intervals, about 95 would contain the parameter and about 5 would not.

Question 35

What is a test statistic?

Answer 35

The number of SE a statistic is away from the hypothesized parameter.

Question 36

What is the golden sentence?

Answer 36

I was curious about a population paramter, but a census was too costly so instead I took a sample and used the data to calculate a statistic and then made an inference about the parameter with that statistic.

Question 37

Where are outliers located in a data set ?

Answer 37

outside the fences. Lower Q1-1.5IQR and upper Q3+1.5IQR

Question 38

When we combine random variables, what do we add?

Answer 38

Add means and add variances. DO NOT ADD ST DEV. You add variances and take the square root of the sum to find combined SD.

Question 39

What does rSy/Sx mean?

Answer 39

slope formula. For each SD in X, you go r SD in y

Question 40

Find P( Z > 1.5) ?

Answer 40

normcdf( 1.5, 9999)

Question 41

What is a critical value?

Answer 41

1 for 68% confidence, 2 for 95 and 3 for 99.7. It is the number of SE you want to reach out in a confidence interval.

Question 42

What are the two sampling distributions we have discussed?

Answer 42

MEANS: N ( mu, sigma/root n) and PROPORTIONS: N ( p, root (pq/n) )