When cluster randomized experiments are analyzed as if units were independent, test statistics for treatment effects can be anticonservative. Hedges proposed a correction for such tests by scaling them to control their Type I error rate. This article generalizes the Hedges correction from a posttest-only experimental design to more common designs…

When performing a meta-analysis unexplained variation above that predicted by within study variation is usually modeled by a random effect. However, in some cases, this is not sufficient to explain all the variation because of outlier or unusual studies. A previously described method is to define an outlier as a study requiring a higher random…

Putative ethnic group differences in various forms of psychopathology may have important theoretical, clinical, and policy implications. Recently, it has been argued that individuals of African descent are more likely to be psychopathic than those of European descent (R. Lynn, 2002). Preliminary evidence from the Psychopathy Checklist: Youth…

The use of hierarchical models in social science research is discussed, with emphasis on causal inference and consideration of the limitations of hierarchical models. The increased use of Gibbs sampling and other Markov-chain Monte Carlo methods in the application of hierarchical models is recommended. (SLD)

Possible relationships between five test examiner characteristics (gender, race, tenure, experience as a test administrator, and experience as a test developer or scorer) and six student achievement scores (reading, writing, language usage, mathematics, science, and social studies) were studied at the school level in a statewide assessment. The…