The biases and mean squared errors of the sample squared multiple correlation coefficient and five adjusted estimators of the population squared multiple correlation are examined. A quadratic estimator and the minimum variance unbiased estimator are also examined. These estimators are compared in terms of absolute bias and mean squared error.…

This article presents an improved approximation formula for the problem of correcting correlation coefficients that arise from range-restricted distributions on either or both the independent and dependent variable. (BS)

Differences between means, variance, and correlation parameter estimates from a full school sample and samples restricted by parental consent were studied with 1,609 students at continuation high schools and 1,192 at traditional high schools. Sample bias due to consent policies may not be a substantive problem, especially if a telephone consent…

An evaluation of the rules-of-thumb used to determine the minimum number of subjects required to conduct multiple regression analyses suggests that researchers who use a rule of thumb rather than power analyses trade simplicity of use for accuracy and specificity of response. Insufficient power is likely to result. (SLD)

Effect sizes have been increasingly emphasized in research as more researchers have recognized that: (1) all parametric analyses (t-tests, analyses of variance, etc.) are correlational; (2) effect sizes have played an important role in meta-analytic work; and (3) statistical significance testing is limited in its capacity to inform scientific…