AP Stats Unit 2

Mean (x̅)

An arithmetic average

Median (M)

The middle of a set of data when arranged from least to greatest

Quartiles

Segments of data divided into four groups, each containing 25% of the data

A set describing a distribution: Minimum, Q1, Median, Q3, Maximum

Five Number Summary

Boxplot

A graph that displays the distribution using the five-number summary

Modified Boxplot

A boxplot that shows outliers as individual points

Variance (s²)

The average of the squared deviations from the mean

Standard Deviation (s)

A measure of spread showing how far data values are from the mean

Range

The difference between the largest and smallest values in a dataset

Nonresistant

A statistic (like the mean) that is affected by extreme values (outliers)

Resistant

A statistic (like the median) that is not significantly affected by extreme values

Interquartile Range (IQR)

The difference between Q3 and Q1; represents the middle 50% of the data

Outlier

A value more than 1.5 × IQR below Q1 or above Q3; does not fit the overall pattern

Degrees of Freedom

The number of independent values that can vary after a statistic is calculated

Variability

A description of how spread out or dispersed a dataset is

Statistic

A numerical measure calculated from a sample

Parameter

A numerical measure calculated from an entire populatio