Using a histogram, the rule of thumb suggests selecting how many intervals across the data range for 87 observations?

Using a histogram, the rule of thumb suggests selecting how many intervals across the data range for 87 observations?

• A. 9
• B. 6
• C. 12
• D. 15

Answer: (A)

A practical rule of thumb for histograms is to choose the number of intervals about equal to the square root of the sample size. This strikes a balance between revealing the distribution’s shape and keeping the bars from becoming too noisy. For 87 observations, sqrt(87) ≈ 9.33, so using 9 intervals across the data range is the typical recommendation. That also gives roughly 9–10 observations per bin on average, which provides a stable, informative histogram. While other rules exist, this question aligns with the square-root approach, hence 9.

A practical rule of thumb for histograms is to choose the number of intervals about equal to the square root of the sample size. This strikes a balance between revealing the distribution’s shape and keeping the bars from becoming too noisy. For 87 observations, sqrt(87) ≈ 9.33, so using 9 intervals across the data range is the typical recommendation. That also gives roughly 9–10 observations per bin on average, which provides a stable, informative histogram. While other rules exist, this question aligns with the square-root approach, hence 9.