The evaluation of intervention effects is an important objective of educational research. One way to evaluate the effectiveness of an intervention is to conduct an experiment that assigns individuals to control and treatment groups. In the context of pretest/posttest designed studies, this is referred to as a control-group pretest/posttest design.…

This paper summarizes three studies that illustrate how application of the three-parameter logistic test model helped solve three relatively intractable testing problems. The three problems are: designing a multi-purpose test, evaluating an multi-level test, and equating a test on the basis of pretest statistics. (Author/JKS)

Regression to the mean (RTM) is often misunderstood. It is demonstrated that artifactual RTM depends fundamentally on the magnitude of measurement error at pretest. Adjustment usually involves estimating the measurement error and determining consequences, but even without adjustment, effects of RTM can be ameliorated. (SLD)

The validity of the equipercentile hypothesis of the Title I Evaluation and Reporting System norm-referenced evaluation model was examined using 3,224 seventh- and ninth-grade students. Findings from confidence interval procedures contradicted the equipercentile hypothesis. There was a pattern of large gains for students not receiving any special…