In this section, we learned about tabular and graphical methods for summarizing qualitative (categorical) data.
Frequency distributions and relative frequency distributions list all the values that a qualitative variable can take, along with the frequencies (counts) or relative frequencies (percents) for each value.
A bar graph is the graphical equivalent of a frequency distribution or a relative frequency distribution. When the rectangles are presented in decreasing order from left to right, the result is a Pareto chart.
Pie charts are a common graphical device for displaying the relative frequencies of a categorical variable. A pie chart is a circle divided into sections (that is, slices or wedges), with each section representing a particular category. The size of the section is proportional to the relative frequency of the category.
Crosstabulation summarizes the relationship between two categorical variables. A crosstabulation is a table that gives the counts for each row-column combination, with totals for the rows and columns.
Data often comes to us already summarized in a table. We can use this tabular data to construct graphs and distributions.
Clustered bar graphs are useful for comparing two categorical variables and are often used in conjunction with crosstabulations.