Observational Studies

William G. Cochran first presented “observational studies” as a topic defined by principles and methods of statistics. Cochran had been an author of the 1964 United States Surgeon General’s Advisory Committee Report, Smoking and Health, which reviewed a vast literature and concluded: “Cigarette smoking is causally related to lung cancer in men; the magnitude of the effect of cigarette smoking far outweighs all other factors. The data for women, though less extensive, point in the same direction (p. 37) .” Though there had been some experiments confined to laboratory animals, the direct evidence linking smoking with human health came from observational or nonexperimental studies.