An ecologic study examining the relationship between per-capita fat consumption and breast cancer rates across 20 countries shows a positive correlation. The main limitation of this study design is:
- A Ecologic fallacy — group-level association may not apply to individuals ✓
- B Selection bias due to non-random sampling
- C Hawthorne effect due to observation
- D Lead-time bias due to early detection
Correct answer: A. Ecologic fallacy — group-level association may not apply to individuals
Explanation
Ecologic fallacy (or aggregation bias) is the central limitation of ecologic studies: an association found at the population level may not reflect individual-level causation, because exposure and outcome are measured on groups, not individuals. Selection bias relates to participant recruitment. Hawthorne effect concerns behavioural change due to observation. Lead-time bias is relevant to screening studies.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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