An ecological study examines the correlation between national per-capita fat consumption and national breast cancer rates and finds r = 0.85. A researcher concludes that high-fat diets cause breast cancer in individuals. This reasoning commits which fallacy?

• A Ecological fallacy (atomistic fallacy in reverse)
• B Ecological fallacy (applying group-level data to individuals) ✓
• C Neyman's bias
• D Simpson's paradox

Explanation

The ecological fallacy occurs when associations observed at the group (population) level are incorrectly attributed to individuals within those groups. Country-level correlations between fat intake and cancer rates cannot establish whether individuals who consume more fat have higher cancer risk — unmeasured confounders and the grouped nature of data prevent individual-level inference. Simpson's paradox refers to reversal of associations when data are aggregated; Neyman's bias is a survivor selection issue in prevalent case studies.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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