A more powerful post hoc multiple comparison procedure in analysis of variance

Scheffe's test (Scheffe, 1953), which is commonly used to conduct post hoc contrasts among k group means, is unnecessarily conservative because it gua rds against an infinite number of potential post hoc contrasts when only a small set would ever be of interest to a researcher. This paper identifies a set of post hoc contrasts based on subsets of the treatment groups and si mulates critical values from the appropriate multivariate F-distribution to be used in place of those associated with Scheffe's test. The proposed met hod and its critical values provide a uniformly more powerful post hoc proc edure.