The estimation of synergy or antagonism
AMERICANJOURNALorEPIDEMIOLOGYCopynght1976byTheJohnsHopkinsUniversitySchoolofHygieneandPublicHealthVol103,No.6PrintedmUSATHEESTIMATIONOFSYNERGYORANTAGONISM1KENNETHJ.ROTHMAN1Theestimationofinteractionoftwovariateshasoftenbeenviewedasaproce-duretobe