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ECOLOGICAL FALLACY

The ecological fallacy is the logical fallacy of interpreting general data too particularly or minutely. An example would be projecting to the level of individuals the generalizations that apply to a population. This fallacy, and the opposite fallacy of generalizing from the particular, have been responsible for some misguided health policies. For example, many epidemiological studies have demonstrated an increased risk of heart disease associated with high-fat diets, cigarette smoking, and lack of exercise; but not everyone who exhibits these behaviors necessarily dies of a heart attack—and it is a mistake to blame such people if they experience a heart attack because many other factors could precipitate such an event. When a relationship was found between drinking water hardness and a reduced risk of dying from heart disease, some public health authorities suggested that municipal water supplies should be artificially hardened by adding calcium or magnesium sulfate, although there was no direct evidence whatever that this would have any real health effect. It is important for those implementing public health policies to guard against this fallacy when transforming theoretical models and scientifically gathered data into real-world policy.

JOHN M. LAST

(SEE ALSO: Data Sources and Collection Methods; Planning for Public Health; Policy for Public Health)