AP Statistics Unit 1: Exploring Data

Distribution

Distribution

The values a variable takes on and how often it takes on those values

Variable

A recorded characteristic of an individual

Categorical Variable

When we place an individual into categories or groups

Frequency

How many times a variable is recorded (counts)

Relative Frequency

How many times a variable is recorded (%)

Pie Chart

Relative frequency compared to a whole

Bar Chart

Rectangular bars that don't touch

Segmented Bar Chart

Useful when comparing two groups

Shape

Describes how the data looks on a graph

Symmetric

The values on either side of the mean or median are roughly equal. (Mean = Median)

Skewed Left

The left tail of the graph is longer than the right (Mean<Median)

Skewed Right

The right tail of the graph is longer than the left (Mean>Median)

Uniform

Shows up as a straight horizontal line on a graph where are outcomes are equally likely

Unimodal

Has one peak

Bimodal

Has two peaks

Multimodal

Has multiple peaks

Quantitative Variable

A variable where the data represents numerical amounts

Common graphs

: dot plot, box plot, stem plot, histogram

Unusual Points

Points that are unusually small or large compared to the whole group

Mean

The average

Median

Halfway point

Spread

The difference from the lowest score in the distribution to the highest score.

Interquartile Range

Represents the middle 50% of the data

Standard Deviation

Average distance from the mean

Range

Maximum - minimum

Comparing distributions

Higher, lower, similar (comparing words)

5-Number Summary

Min, Q1, Median, Q3, Max

Standard Deviation

A common measure of spread (Always positive, average distance from the mean)

Percentile

The percent of observations at or below a value

Quartile 1

The bottom 25% of the data

Quartile 3

The value where 75% of data points are found equal to or below when arranged in an increasing order

Median equation

(n+1)/2

IQR

Q3-Q1