Monte Carlo studies explored the sampling characteristics of Cohen's d and three approximations to Cohen's d when used as average effect size measures in meta-analysis. Reviews of 10, 100, and 500 studies (M) were simulated, with degrees of freedom (df) varied in seven steps from 8 to 58. In a two independent groups design, samples were obtained…

A population data set was randomly generated from which a random sample was drawn. This sample was randomly divided into two data sets, one of which was used to generate parameter estimates, which were then used in the second data set for cross-validation purposes. The best variable subset models were compared between the two data sets on the…

The inherent methodological problem in conducting research at multiple sites is how to best derive an overall estimate of program impact across multiple sites, best being the estimate that minimizes the mean square error, that is, the square of the difference between the observed and true values. An empirical example illustrates the use of the…

The merits of the multilevel model for educational research and its uses for school effectiveness research are considered. The main goal of the paper is to establish what intelligent applications of multilevel models can do, helping researchers decide what they must do to make a rational choice between models. Multilevel models are random line…