Partitioning is justified if there are at least 40 individuals within each subclass or if there are clear clinical reasons.

• A. At least 40 per subclass only
• B. Clear clinical reasons only
• C. At least 40 per subclass or clear clinical reasons
• D. Neither condition

Answer: (C)

Partitioning into subclasses is justified when you have enough data to support reliable comparisons, and there are also situations where differences are clinically meaningful even if the numbers are smaller. A common rule of thumb is about 40 individuals per subclass, which helps ensure estimates of means, proportions, and differences are stable and not overly influenced by random variation. But if there is a clear clinical reason that a subgroup should be considered separately—because it behaves differently in prognosis, treatment response, or outcomes—partitioning is warranted even when some groups don’t meet that 40-per-subclass threshold. Therefore, you justify partitioning if either condition is met: enough data in each subclass or a strong clinical rationale. If you require both, you’d miss legitimate scenarios where one condition holds. If neither condition applies, partitioning isn’t justified.