In an ecological study examining mean national salt consumption vs age-adjusted hypertension prevalence across 20 countries, a strong positive correlation (r=0.82) is observed. Which fallacy must be specifically cautioned against when interpreting this finding?

• A Gambler's fallacy
• B Base rate fallacy
• C Ecological fallacy (atomistic fallacy in reverse) ✓
• D Post hoc ergo propter hoc fallacy

Explanation

Ecological fallacy (or ecological bias) is the error of assuming that relationships observed at the group/aggregate level (countries) apply to individuals. A high national salt intake correlated with high national hypertension prevalence does not prove that individuals who eat more salt have hypertension — the association may be confounded at the country level. This is the fundamental limitation of ecological studies. The 'atomistic fallacy' is the reverse error (inferring group properties from individual data).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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