The ecological fallacy can occur in the field of epidemiology when individual risk factors or health outcomes are inferred from population-level data. Consider the following example:
Population-level data: Research indicates that Japan has one of the lowest rates of heart disease globally. The low incidence of heart disease is commonly attributed to healthy lifestyle choices.
Ecological fallacy inference: A graduate student conducts a study on a small group of test subjects from Japan and assumes that each test subject has a very low risk of heart disease.