In an ecologic study, a positive correlation is found between national fat consumption and breast cancer mortality. Which fundamental limitation of ecologic studies MOST directly prevents causal inference from this finding?

• A Observer bias
• B Ecologic fallacy (aggregation bias) ✓
• C Incubation period bias
• D Response bias

Explanation

The ecologic fallacy is the error of inferring individual-level associations from group-level (aggregate) data. The group or country with higher average fat intake may not be the same individuals who develop breast cancer — the correlation at the population level does not imply the same association at the individual level. This is the defining limitation of ecologic studies and is distinct from information bias or observer bias, which affect individual-level measurement accuracy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.