If scores range from 28 to 72, what is the best interval width for a grouped frequency distribution?

If scores range from 28 to 72, what is the best interval width for a grouped frequency distribution?

• A. 5 points
• B. 7 points
• C. 10 points
• D. 12 points

Answer: (A)

Choosing interval width for a grouped frequency distribution is about balancing detail with readability. With scores ranging from 28 to 72, the data span a 44‑unit range. You want enough class intervals to reveal the distribution’s shape without making the histogram too busy, but not so few that important features are smoothed over. A sensible target is around five to ten intervals; that way you can see where scores cluster and whether the data are skewed or multimodal. An interval width that yields about nine intervals across the 28–72 range provides this balance: it keeps the classes small enough to show variation but large enough to keep the chart readable. Wider choices would compress the data into too few classes, hiding detail, while narrower choices would produce many sparse or noisy classes. So the best width is the one that gives roughly nine intervals across the range, offering a clear and informative picture of the distribution.

Choosing interval width for a grouped frequency distribution is about balancing detail with readability. With scores ranging from 28 to 72, the data span a 44‑unit range. You want enough class intervals to reveal the distribution’s shape without making the histogram too busy, but not so few that important features are smoothed over. A sensible target is around five to ten intervals; that way you can see where scores cluster and whether the data are skewed or multimodal. An interval width that yields about nine intervals across the 28–72 range provides this balance: it keeps the classes small enough to show variation but large enough to keep the chart readable. Wider choices would compress the data into too few classes, hiding detail, while narrower choices would produce many sparse or noisy classes. So the best width is the one that gives roughly nine intervals across the range, offering a clear and informative picture of the distribution.