A generalization of the usual random-effects model based on trimmed means is proposed. The resulting test of no differences among J randomly sampled groups has advantages in terms of Type I errors and can yield gains in power when distributions have heavy tails and outliers. (SLD)

Describes a technique for statistically comparing bibliometric models and illustrates its use with two examples using Lotka's hypothesis of author productivity and one example using library circulation frequencies. Topics discussed include nested statistical models, analysis of variance, regression, log-linear models, and the likelihood ratio…

This study investigated the robustness of the James second-order test (James 1951; Wilcox, 1989) and the univariate F test under a two-factor fixed-effect analysis of variance (ANOVA) model in which cell variances were heterogeneous and/or distributions were nonnormal. With computer-simulated data, Type I error rates and statistical power for the…

In educational research, nonessential factors are commonly ignored and when accounted for, they are often treated statistically as fixed effects. Yet many researchers in these situations generalize their findings beyond the specific levels selected; however, the analyses may require treating the factor as a random effect. Such inappropriate…