POWER OF UNWEIGHTED AND WEIGHTED VERSIONS OF SIMULTANEOUS AND SEQUENTIAL MULTIPLE-COMPARISON PROCEDURES

The authors investigate the relative power of unweighted and weighted versions of simultaneous and sequential Bonferroni procedures. The unw eighted simultaneous procedure is represented by the standard Bonferro ni; the unweighted sequential methods are from S. Helm (1979) and G. H ommel (1988); the weighted simultaneous procedure comes from R. Rosent hal and D. B. Rubin (1984); and the weighted sequential method is also from S. Helm (1979). These are applied to a complete set of C = 3 ort hogonal contrasts defined by 4 treatment groups. The authors present p ower estimates for small, medium, and large effects in various effect and weighting configurations. They discuss factors affecting the relat ive power of these methods and present statistical evidence that stren gthens a case against weighted procedures built on methodological subj ectivity issues.