1.4 Graphical Representations for One Categorical Variable

Construct categorical one-variable graphical representations.

• Bar charts, also called bar graphs, display frequencies (counts) or relative frequencies (proportions) for the categories of a single categorical variable. Each bar on a bar chart represents a category of the categorical variable of interest. The height or length of each bar corresponds to the frequency or relative frequency of the observational units in each category.
• Pie charts are used to display frequencies (counts) or relative frequencies (proportions) for categorical data. Each slice on a pie chart represents a category of the categorical variable of interest. The area of each slice, as a fraction of the total area, corresponds to the relative frequency of observational units falling within each category. The sum of the slices’ areas together will equal 1, or 100% of the total area.

Justify a claim using categorical one-variable graphical representations.

• Graphical representations of a categorical variable reveal information that can be used to justify claims about the variable in context.

Compare multiple categorical one-variable tabular and graphical representations.

• Frequency and relative frequency tables, bar charts, and pie charts can be used to compare two or more data sets in terms of the same categorical variable.