In order to really assess of asbetos exposure without smoking potentially confounding the results, the populations were stratified by smoking status. Of those who developed lung cancer, 75 were smokers exposed to asbestos while 10 were non smoker who were not exposed to asbestos. among those who did not develop lung cancer, 20 2343 smokers exposed to asbestos while 72 were neither smokers nor exposed to asbestos. Complete 2x2 tables