ESTIMATION OF SYNERGY OR ANTAGONISM

In describing cause and effect relationships, synergy or antagonism is evaluated to elaborate the determinants of a given effect. Risk factors are probable causes in the elaboration of disease etiology; the point and interval estimation for a parameter to quantify interaction of the causes is discussed. The index of interaction is the ratio of the joint effect to the theoretical joint effect under independence; its estimation is discussed. A case control study of the effects of smoking and alcohol consumption on risk of oral cancer is discussed as an example.