After recording final grades A through E for 26 students, which graph should be used to display the grade distribution?

• A. A bar graph
• B. A histogram
• C. A polygon
• D. Either a histogram or polygon

Answer: (A)

When you’re displaying counts for distinct categories like final grades A through E, the data are categorical and you want to compare how many students fall into each category. A bar graph fits this perfectly: each grade is its own category and the height of the bar shows the number of students who earned that grade. This makes it easy to see which grades are most or least common at a glance.

A histogram, by contrast, is meant for numerical data that are grouped into continuous intervals, so it would imply a numeric scale and distance between categories that doesn’t exist for letter grades. A polygon (frequency polygon) is typically used for numerical distributions by connecting midpoints of class intervals, which isn’t appropriate for discrete letter grades. Therefore, the bar graph is the clearest and most appropriate choice for this grade distribution.