ap stats things to remember

name 2 measures of center

mean and median

name 3 measures of spread

standard deviation, iqr, range

what is variance

standard deviation squared (σ²)

when is standard deviation 0

when all the data is the same

outlier test formula

> Q3 + 1.5 IQR

< Q1 - 1.5 IQR

right skew

long tail on right side, mean > median

left skew

long tail on left side, mean < median

CUSS

center, unusual features, shape, spread

basic z score formula

how many standard deviations an element is from the mean.

blocking reduces

variation - ensures differences in groups are due to treatment alone

randomization reduces

bias - controls variables we don’t know

formula for 1 samp T int for a sample mean

used to estimate population mean from a sample mean

formula for 1 prop z interval

used to estimate a population proportion from a sample proportion.

type I error

rejecting a TRUE H₀

type II error

failing to reject a FALSE H₀

power

probability of correctly rejecting H₀

alpha (α)

probability of a type I error (rejecting a true H₀)

test for independent variables

P(A) x P(B) = P(A and B)

P(A|B) = P(A)

BINS (binomial condition)

Binary (success/fail)

Independent

Number of trials is fixed

Same probability for each trial

confidence level is ____ to margin of error

proportional (CI goes up when ME goes up)

when population variance is known and when n > 30

1 prop z test

formula for

1 mean T test

standard deviation formula for:

2 mean T test / interval

standard deviation for:

2 prop Z test

standard deviation for:

2 prop Z int

SOFA for scatterplots/correlation

Strength (r or r²)

Outliers

Form (linear or exponential)

Association (pos or neg)

P(A∪B) =

P(A) + P(B) − P(A∩B)

P(A∩B) =

P(A) x P(B) if independent

P(A’) =

1 – P(A)

P(A|B) =

P(A∩B) / P(B)

formula for binomial mean

np

n = number of trials

p = probability of success

formula for binomial variation

np(1-p)

n = number of trials

p = probability of success

formula for geometric mean

1/p

p = probability of success

formula for geometric variance

(1–p)/p_²

p = probability of success