Which of the following graphs is least effective for displaying categorical data?

The least effective graph for displaying categorical data is a scatter plot because it is designed to show the relationship between two continuous variables, rather than displaying categories and their respective values. In a scatter plot, each point represents a data pair, which makes it ideal for showcasing trends or correlations within numerical data, rather than summarizing or comparing distinct categories.

On the other hand, bar graphs, pie charts, and column charts are specifically tailored for categorical data representation. Bar graphs use rectangular bars to illustrate the frequency or value of categories, allowing for easy comparison between them. Column charts function similarly but with vertical bars. Pie charts provide a visual breakdown of parts to a whole, displaying how each category contributes to an overall total. These formats provide clear, comparative insights into categorical data, making them highly effective for that purpose.