Developed a full maximum likelihood method for obtaining joint estimates of variances and correlations among continuous and polytomous variables with incomplete data that are missing at random with an ignorable missing mechanism. Simulation results and an empirical example illustrate the approach. (SLD)

Four theories of the human conceptual system--semantic memory, exemplar models, feed-forward connectionist nets, and situated simulation theory--are characterized and contrasted on five dimensions. Empirical evidence is then reviewed for the situated simulation theory and conclusions are discussed. (Author/VWL)

Discusses the use of inverted files in information retrieval systems and proposes a document identifier reassignment method to reduce the average gap values in an inverted file. Highlights include the d-gap technique; document similarity; heuristic algorithms; file compression; and performance evaluation from a simulation environment. (LRW)

Studied the Type I error rate and the power of a number of new and existing tests of fit to the three-parameter logistic model. Simulation study results show that all the tests except one have a Type I error rate acceptably close to the nominal significant level and good power to detect the model violations at which they are targeted. (SLD)

Proposed and evaluated a modified version of the maximum Fisher information (MFI) criterion called the nearest-neighbors (NN) criterion. Simulation study results show that NN procedure improved to a moderate extent the undesirable item exposure rates associated with the MFI criterion and keeps sufficient precision in theta estimates. (SLD)

Studied a multiple group model with ordinal categorical observed variables that are manifestations of underlying normal variables. Proposed to apply across-group stochastic constraints on thresholds to identify the model and used a Bayesian approach to analyze the model. Simulation findings and the analysis of a real data set show the usefulness…

Developed a method, based on the conditional maximum likelihood principle, for establishing latent change classes in dichotomous data. Simulation studies and a real data set from an earlier study illustrate the method of parameter estimation. (SLD)

Developed methods for testing whether or not patterns of incomplete data represent samples from a single population. Results from a simulation study show that the generalized least squares test of homogeneity of means performed close to an ideal Type I error rate for most of the conditions. The generalized least squares test of homogeneity of…

Studied the statistical properties of the K-index (P. Holland, 1996) that can be used to detect copying behavior on a test through a simulation study of the use of the K-statistic with small, medium, and large datasets. Also compared the Type I error rate and detection rate of this index with those of the copying index (J. Wollack, 1997).…

Through simulation, showed that a multivariate test of interactions for aligned ranks in a split-plot design controlled Type I error rates for nonnormal data with nonspherical covariance structures. This method also performed well in the presence of a strong repeated measures main effect and demonstrated more statistical power than parametric…

Results of this simulated study indicate that, when unidimensional stimulus sets are scaled in two dimensions using a rational starting configuration, the nature of the two-dimensional configuration can indicate the general form of the function mapping psychological dissimilarity--represented as distance in the scaling model--onto the observed…

Simulated test data (N=864 artificial data sets) with four different error conditions were used to study the recovery characteristics of the beta-flexible clustering method. Conditions under which the beta-flexible method provides good recovery are discussed. (SLD)

Three-dimensional response surface plots are presented for several hierarchical clustering methods and simulated core group data structures. Influence patterns explain some results from previous validation research on clustering methods and have significant implications for the choice of clustering methods in empirical research. (SLD)

In Varimax rotation, permutations and reflections can give rise to the phenomenon that certain pairs of columns are consistently skipped in the iterative process, causing Varimax to terminate at a nonstationary point. This skipping phenomenon is demonstrated, and how to prevent it is described. (SLD)

Fundamental concepts of Gaussian Recognition Theory are reviewed, and one of the major theorems used to test for perceptual independence among stimulus dimensions is disputed through a relatively simple counterexample. An amended version of the theorem, Theorem 4, is offered, and a simulation demonstrates its utility. (SLD)