Objectives: Group-randomized designs are well suited for studies of professional development because they can accommodate programs that are delivered to intact groups (e.g., schools), the collaborative nature of professional development, and extant teacher/school assignments. Though group designs may be theoretically favorable, prior evidence has…

Describes and compares useful and unified power formulas for analysis of covariance and change-score analyses, indicating the implications of each for sample size requirements. Contains practical recommendations for evaluations and outlines a simple spreadsheet approach. (SLD)

The use of multiple regression for analyzing data from the regression-discontinuity design (RDD) is examined, considering the effects of random measurement error in the pretest, treatment-effect interactions, and curvilinearity in the regression analysis of RDD. Three sets of conditions of increasing generality are reviewed. (SLD)

A conceptual approach and a set of computer simulations are presented to demonstrate that random measurement error in the pretest does not bias the estimate of the treatment effect in the regression-discontinuity design. Focus is on the case of no interaction between pretest and treatment on posttest. (SLD)

High intercommunity variation in adolescent smoking precluded detection of effects of mass media campaigns on initiation of cigarette smoking in a study with a final sample of 1,637 adolescent subjects. Implications for studies using the individual as unit of analysis and the community as unit of randomization are discussed. (SLD)