流行病学家和公共卫生工作者已提出几种归因危险度(Attributable risk)的指标。已知P_1=接触组的发病率,P_2=非接触组的发病率。Berkson提出以两者之差,P_1-P_2,作为指标。而Sheps的相对差,(P_1—P_2)/(1—P_2),则侧重于接触组中归因于接触的发病率这一分量。MacMahon等将归因危险度定义为接触组中可用接触解释的病例的部份,并提出一个 Epidemiologists and public health workers have proposed several indicators of Attributable risk. It is known that P 1 = incidence of contact group, P 2 = incidence of non-contact group. Berkson proposed the difference between the two, P_1-P_2, as an indicator. The relative difference in Sheps, (P 1 -P 2) / (1-P 2), focuses on the component attributable to the incidence of exposure in the contact group. MacMahon et al. Defined attribution of risk as part of the available contact interpretation in the contact group and proposed a