Analyzing Categorical Data

Frequency Table

shows the number of individuals having each value

Relative Frequency Table

shows the proportion or precent of individuals having each value

Bar Graph

Shows each category as a bar. The heights of the bars show the category frequencies or relative frequency

Pie Chart

shows each category as a slice of the “pie”. The areas of the slices are proportional to the category frequencies or relative frequencies

Two-way table

a table of counts that summarizes data on the relationship between two categorical variables for some group of individuals

Marginal relative frequency

gives the percent or proportion of individuals that have a specific value for one categorical variable

Joint relative frequency

gives the percent or proportion of individuals that have a specific value for one categorical variable and a specific value for another categorical variable

Conditional relative frequencies

gives the percent or proportion of individuals that have a specific value for one categorical variable among individuals who share the same value of another categorical variable (the condition)

side-by-side bar graph

displays the distribution of a categorical variable for each value of another categorical variable. The bars are groups together based on the values of one of the categorical variables and placed side-by-side

Segmented bar graph

displays the distribution of a categorical variable as segments of a rectangle, with the rea of each segment proportional to the percent of individuals in the corresponding category

Mosaic plot

a modified segmented bar graph in which the width of each rectangle is proportional to the number of individuals in the corresponding category

Association

helps us know if the value of one variable helps predict the value of the other