Growth mixture modeling has gained much attention in applied and methodological social science research recently, but the selection of the number of latent classes for such models remains a challenging issue, especially when the assumption of proper model specification is violated. The current simulation study compared the performance of a linear…

Differences between per experiment (PE) and experimentwise (EW) error rates were studied through simulation for several multiple-comparison procedures for both pairwise comparisons and planned contrasts. Results suggest ways to control PE rates through new multiple-comparison procedures that maximize experimental power while controlling Type I…

Proposes a method for post hoc contrasts based on subsets of treatment groups, and simulates critical values from the appropriate multivariable F-distribution to be used in place of those associated with Scheffe's test (H. Scheffe, 1953). The proposed method and its critical values provide a uniformly more-powerful post hoc procedure. (SLD)

Two strategies, derived from J. P. Schaffer (1986), were compared as tests of significance for a complete set of planned orthogonal contrasts. The procedures both maintain an experimentwise error rate at or below alpha, but differ in the manner in which they test the contrast with the largest observed difference. One approach proceeds directly to…

The challenge of multiple comparisons is to maximize the power for answering specific research questions, while still maintaining control over the rate of Type I error. Several multiple comparison procedures have been suggested to meet this challenge. The stagewise protected procedure (SPP) of A. J. Klockars and G. R. Hancock tests null hypotheses…