AP Statistics Unit 1

Individuals

Individuals are the smallest units represented by data.

Variable

A variable is any characteristic of an individual.

The two types of variables

1. Categorical variables

2. Quantitative variables

Categorical variables

Categorical variables place an individual into one of several groups

Quantitative variables

Quantitative variables have numerical values for which averages are meaningful

Advice: a numeric variable is not necessarily quantitative. Consider student ID numbers.

Frequency table

A frequency table shows the counts or frequencies of variables.

Relative frequency table

A relative frequency table displays the percentages (relative frequencies) of a variable.

Bar Graphs

• are used for categorical data

• have spaces between the bars

Pie charts

• are used for categorical data

• represent portions of the whole

Two-way table

A two-way table summarizes the data on the relationship between two categorical variables.

Conditional distribution

Conditional distribution considers the distribution of a subset of the group

Marginal distribution

Marginal distribution considers the distribution of the whole group

Side by side bar graph

The different categories are displayed beside each other, with gaps between each value on the x-axis.

Segmented bar graph

• A segmented bar graph shows different categories in each bar with the height of each category corresponding to its y-value

• The segmented bar graph can be obtained by stacking the bars in the side-by-side bar graph

Mosaic plot

• The bar widths in the mosaic plot are proportional to the number of respondents

Association

There is an association between two variables if knowing the value of one variable helps us predict the value of the other.