When analyzing results across different groups, which approach is recommended?

• A. Subset by group, compute statistics for each group, then compare results.
• B. Combine all groups and compute a single overall statistic.
• C. Compare only the largest group.
• D. Ignore group labels and treat all data as one.

Answer: (A)

When results can differ across groups, analyze by group first. Compute the statistic for each group (for example, the mean, median, and spread) and then compare these group-specific results. This approach reveals whether effects or patterns are present in all groups or only in some, and it helps you see how group characteristics influence outcomes. Pooling all data into one overall statistic can hide important differences, and might even give a misleading picture (like Simpson’s paradox). By examining each group separately, you respect potential heterogeneity and can identify where differences truly lie. Ignoring group labels or focusing only on the largest group ignores variation and can bias conclusions toward that group’s experience.