A study compares regional rates of salt consumption with hypertension prevalence across 20 Indian states and finds a strong positive correlation (r = 0.82). A policy maker concludes that individuals who consume more salt have higher rates of hypertension. This reasoning exemplifies:
- A Confounding
- B Selection bias
- C Ecological fallacy ✓
- D Information bias
Correct answer: C. Ecological fallacy
Explanation
The ecological fallacy (atomistic fallacy) occurs when associations found at a group (ecological) level are incorrectly inferred to apply at the individual level. The correlation observed between state-level salt consumption and hypertension rates cannot validly be applied to individual behavior-disease relationships because within-state variation is ignored and confounders at state level (diet, genetics, healthcare access) may explain the correlation. This is a fundamental limitation of ecological study designs.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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