A comment on the importance of numerical evaluation of analytic solutions involving approximations.
An analytic solution proposed by Senn (1) for removing the effects of covariate imbalance in controlled clinical trials was subjected to Monte Carlo evaluation. For practical applications of his derivation, Senn proposed substitution of sample statistics for parameters of the bivariate normal model. Unfortunately, that substitution produces severe distortion in the size of tests of significance for treatment effects when covariate imbalance is present. Numerical verification of proposed substitutions into analytic models is recommended as a prudent approach.
University of Texas Medical School, Houston 77225.
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Overall
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Starbuck
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Doyle
D000704:Analysis of Variance; D018849:Controlled Clinical Trials as Topic / Q000706:statistics & numerical data*; D015233:Models, Statistical; D009010:Monte Carlo Method; D011336:Probability; D011897:Random Allocation