Which data display tool is used to display discrete categories?

• A. Line graph
• B. Pie chart
• C. Bar graph
• D. Scatter plot

Answer: (C)

When you’re showing discrete categories, a bar graph is the best choice because each category has its own distinct bar, making it easy to compare how large or frequent each category is without implying any order or smooth change between them. The height or length directly represents the magnitude for that category, and the separation between bars visually reinforces that the groups are separate.

Line graphs are geared toward continuous data that change over time or another continuous variable, highlighting trends rather than category-by-category differences. Pie charts display portions of a whole as slices, which works for proportions but becomes hard to read when there are many categories or small differences. Scatter plots map two continuous variables to explore relationships, not to compare discrete categories. In quality improvement, bar graphs are the straightforward way to compare counts or percentages across distinct categories.