Introduces a new algorithm for obtaining exact person fit indexes for the Rasch model. The algorithm realizes most tests for a general family of alternative hypotheses, including tests concerning differential item functioning. The method is also used as a goodness-of-fit test in some circumstances. Simulated examples and an empirical investigation…

Computer simulations used to compare the Mahalanobis distance procedure with the Andrews-Pregibon statistic for identifying multivariate outliers result in the conclusion that the choice of procedure is not critical, since both identified valid data points as outliers. Results with false outliers as the dependent variable suggest the importance of…

The primacy model is presented as a new model of serial recall. This model stores order information by means of the assumption that the strength of activation of successive list items decreases across list position to form a primary gradient. The model produces accurate simulation of the effects of word length, list length, and phonological…

Discusses a rank-ordering exercise designed to highlight evaluation issues involved in development of simulation training activities. The rank-ordering exercise raised awareness of internal and external validity issues, and highlighted the need for evaluation "checks" to be made during the planning stages of any research of consultancy…

Computer simulation indicated that reliability increased with the degree of similarity between underlying and observed distributions when the observed categorical distribution was deliberately constructed to match the shape of the underlying distribution of the trait being measured. Reliability also increased with correlation among variables and…

Using simulation, studied the influence of each of 12 imputation methods and 2 methods using the EM algorithm on the results of maximum likelihood factor analysis as compared with results from the complete data factor analysis (no missing scores). Discusses why EM methods recovered complete data factor loadings better than imputation methods. (SLD)

Studied the efficacy of two improvement-over-chance or "I" effect sizes derived from predictive discriminant analysis and logistic regression analysis for two-group univariate mean comparisons through simulation. Discusses the ways in which the usefulness of each of the indices depends on the population characteristics. (SLD)

Compared student ability estimates with their true abilities under different rater scoring designs and differentially weighted composite scores through simulation. Results indicate that the spiraled rater scoring design without modeling rater effects works as well as the nested design in which rater tendencies are modeled. (SLD)

Describes available variance component tests and presents three new score tests. One test uses the asymptotic normal distribution of the test statistic as a reference distribution; the others use a Satterthwaite approximation for the null distribution of the test statistic. Evaluates the performance of these tests through Monte Carlo simulation.…

Examined the effect of test purification in detecting differential item functioning (DIF) by means of polytomous extensions of the Raju area measures (N. Raju, 1990) and the Lord statistic (F. Lord, 1980). Simulation results suggest the necessity of using a two-stage equating purification process with the Raju exact measures and the Lord statistic…

Evaluated coefficient alpha under violations of two classical test theory assumptions: essential tau-equivalence and uncorrelated errors through simulation. Discusses the interactive effects of both violations with true and error scores. Provides empirical evidence of the derivation of M. Novick and C. Lewis (1993). (SLD)

Combines procedures for single-level mediational analysis with multilevel modeling techniques to test mediational effects in clustered data appropriately. Compared, through simulation, the performance of these multilevel mediational models with that of single-level models in clustered data with various real-world characteristics. (SLD)

Compared effect sizes based on simulated groups for the one-parameter and three-parameter logistic item response theory (IRT) models. Data fit the three-parameter model much better, but there were only minimal differences between the effect sizes based on different models. (SLD)

Examined the effects of ignoring multilevel data structures in nonhierarchical covariance modeling using a Monte Carlo simulation. Results suggest that when the magnitudes of intraclass correlations are less than 0.05 and the group size is small, the consequences of ignoring the data dependence within the multilevel data structures seem to be…

Studied sample sizes for confidence intervals on the increase in the squared multiple correlation coefficient using simulation. Discusses predictors and actual coverage probability and provides sample-size guidelines for probability coverage to be near the nominal confidence interval. (SLD)