AP Stats lesson 1

3 measures of central tendency

mean, median, mode

Mean

NOT resistant to outliers

(always quantitative)

Median & mode

resistant to outliers

Categorical variable

uses labels or names (proportions/percentages)

Quantitative variable

operated with add, mult, subt, or division

Continuous variable

take an infinite # of values between min & max

Discrete variable

take finite # values between min & max

Univariate data

uses only 1 variable

Bivariate data

uses 2 varaibles

Population

includes everyone in your group of interest

Sample

subset of the population (can be less, equal, greater than the pop.)

Simple Random Sample (SRS)

every group of size n is equally likely to be chosen

Median

should use to describe a data set when the data set includes outliers

Population mean

μ

Population proportion

p

Population SD

σ

Sample mean

x̄

Sample proportion

p̂

Sample SD

s

measures of variability

• range

• iqr

• sd

• variance

SD

distance each data point is away from the mean

measures of position

• percentiles

• quartiles

• z scores

Z score

• has no units

• standardized score

• tells you how many sds a data point is AWAY from the mean

Z=0

point is the mean

Z=3

point is 3 sds above the mean

Z=-2

point is 2 sds below the mean

Z score formula

(x – μ) / σ

Outliers formula

• x<Q1-1.5(IQR)

• x>Q3+1.5(IQR)

Deviation sum of squares formula

Σ(X - μ)²