Greenland S
Stat Med. 1987 Mar;6(2):193-5. doi: 10.1002/sim.4780060211.
It is well known that comparisons of indirectly adjusted statistics, such as standardized morbidity ratios (SMRs), can be biased when the joint effect of the study exposure and the covariates is not multiplicative. This paper describes a related bias in SMR comparisons, one that can arise if the total study population is used as the referent. This bias can occur even if the exposure-covariate effects are multiplicative.
众所周知，当研究暴露因素和协变量的联合效应不是相乘形式时，间接调整统计量（如标准化发病比，SMR）的比较可能会产生偏差。本文描述了SMR比较中一种相关的偏差，即如果将整个研究人群用作参照时可能出现的偏差。即使暴露-协变量效应是相乘形式，这种偏差也可能发生。
