In reply: Covariate adjustment for prognostic baseline characteristics may decrease the sample size

Anthony C Keech and Val J Gebski
Med J Aust 2003; 178 (7): . || doi: 10.5694/j.1326-5377.2003.tb05239.x
Published online: 7 April 2003

In reply: While we agree that covariate adjustment during analysis can be a potential mechanism for reducing sample size (even when there is no imbalance in the important covariate levels between the treatment groups), unless such analyses are prospectively planned then they will not allow valid statistical inference. This is because post-hoc adjustment is an exploratory procedure and may have involved examining any number of potential covariates.

  • Anthony C Keech
  • Val J Gebski



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