epidemiological study A human study of diseases in populations of humans or other animals, specifically how, when and where they occur. Epidemiological studies can never prove causation, epidemiological evidence can only show that this risk factor is correlated with a higher incidence of disease in the population exposed to that risk factor. The higher the correlation the more certain the association, but it cannot prove the causation. A study of the populations and demographic of the avian flu. PERSON: Karen Corday http://pmep.cce.cornell.edu/profiles/extoxnet/TIB/epidemiology.html epidemiological study human subject study