Chapter 1 Definitions

Individual

An object described in a set of data. Individuals can be people, animals, or things.

Variable

An attribute that can take different values for different individuals.

Categorical variable

Assigns labels that place each individual into a particular group, called a category.

Quantitative variable

Takes number values that are quantities--counts or measurements.

Univariate Data

Data that involves only one measurement on each object.

Bivariate data

Data that involves two measurements on each object.

Discrete variables

Quantitative variables that result from counting and take a fixed set of possible values with gaps.

Continuous variables

Quantitative variables that result from measuring and can take any value in an interval on the number line.

Distribution

Describes what values the variable takes and how often those values occur.

Frequency table

A table showing the number of individuals having each value.

Relative frequency table

A table showing the proportion or percent of individuals having each value.

Cumulative Frequency

The total number of observations less than or equal to a specified value.

Frequency Distribution Table

A table giving all possible values of a variable and their frequencies.

Bar Graph

A graph showing each category as a bar, with heights representing frequencies or relative frequencies of categorical data.

Pie chart

A circular chart that shows each category as a slice, with areas proportional to the category frequencies.

Two-way table

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

Marginal Relative Frequency

The percent or proportion of individuals that have a specific value for one categorical variable.

Joint Relative Frequency

The percent or proportion of individuals that have specific values for two categorical variables.

Conditional Relative Frequency

The percent or proportion of individuals that have a specific value for one categorical variable among those with a specific value of another.

Side by Side Bar Graph

A graph that displays the distribution of a categorical variable for each value of another categorical variable, with bars grouped side by side.

Segmented Bar Graph

A graph displaying the distribution of a categorical variable as segments of a rectangle.

Mosaic Plot

A modified segmented bar graph where the width of each rectangle is proportional to the number of individuals in each category.

Association

Exists between two variables if knowing the value of one helps predict the value of the other.