Permutt T
Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore 21201.
Stat Med. 1990 Dec;9(12):1455-62. doi: 10.1002/sim.4780091209.
Results of a controlled experiment are often adjusted for covariates found by a preliminary test to differ significantly between the treatment and control groups. The resulting test's true significance level is lower than the nominal level. Greater power can be achieved by always adjusting for a covariate that is highly correlated with the response regardless of its distribution between groups.
对照实验的结果通常会针对初步测试中发现的协变量进行调整，这些协变量在治疗组和对照组之间存在显著差异。由此产生的检验的真实显著性水平低于名义水平。无论协变量在组间的分布如何，始终对与反应高度相关的协变量进行调整，可以获得更大的检验效能。
