See TM 501 201-2 for related articles. (MLP)

True effects of the joint dichotomization of two variables are explored, and implications of the correct formulation for generalizations of the results obtained by S. E. Maxwell and H. D. Delaney (1993) are examined. The inflation of apparent effects can occur when only one or two predictor variables is dichotomized. (SLD)

See TM 501 201-3 and EJ 060 883 for related articles. (MLP)

A modification of the SIBTEST procedure to assess differential item functioning (DIF) for two-dimensional test data (i.e., data for tests where two intended abilities are tapped by test items) is described. A small simulation study is carried out to assess the performance of the modified SIBTEST to detect DIF in such two-dimensional data. The…

A concise table is presented based on a general measure of magnitude of effect which allows direct determinations of statistical power over a practical range of values and alpha levels. The table also facilitates the setting of the research sample size needed to provide a given degree of power. (Author/CM)

Psychophysicists neglect to consider how error should be characterized in applications of the power law. Failures of the power law to agree with certain theoretical predictions are examined. A power law with lognormal product structure is proposed and approximately unbiased parameter estimates given for several common estimation situations.…

This study shows that the test statistic for Analysis of Covariance (ANCOVA) has a noncentral F-districution with noncentrality parameter equal to zero if and only if the regression planes are homogeneous and/or the vector of overall covariate means is the null vector. The effect of heterogeneous regression slope parameters is to either increase…

Investigates the Tukey statistic for the empirical probability of a Type II error under numerous parametric specifications defined by Cohen (1969) as being representative of behavioral research data. For unequal numbers of observations per treatment group and for unequal population variancies, the Tukey test was simulated when sampling from a…

Describes a computer program for calculating the power of the F-test. Approach is based upon two independent approximations-- a normalization of the non-central F distribution and an integration of the normal distribution. Comparison of the calculated values of power with exact values revealed a high degree of accuracy. (Author/RC)

Errors of misclassification associated with two concept acquisition criteria and their effects on the actual significance level and power of a statistical test for sequential development of these concepts are presented. Explicit illustrations of actual significance levels and power values are provided for different misclassification models.…

Provided initial assessment of the statistical power of rehabilitation counseling research published in selected rehabilitation journals. From 5 relevant journals, found 32 articles that contained statistical tests that could be power analyzed. Findings indicated that rehabilitation counselor researchers had little chance of finding small…

See TM 501 202-3 and EJ 060 883 for related articles. (MLP)

Power analysis is in essence a technique for estimating the probability of obtaining a specific minimum observed effect size. Power analysis techniques are applied to research planning problems in test reliability studies. A table for use in research planning and hypothesis testing is presented. (Author)

J. P. Shaffer has presented two tests to improve the power of multiple comparison procedures. This article described an algorithm to carry out the tests. The logic of the algorithm and an application to a data set are given. (SLD)

Although the primary responsibility rests with the authors of articles reporting nonsignificant results to demonstrate the worth of the results by discussing the power of the tests, consumers should be prepared to conduct their own power analyses. This article demonstrates the use of power analysis for the interpretation of nonsignificant…