As a global measure of precision, item response theory (IRT) estimated reliability is derived for four coefficients (Cronbach's a, Feldt-Raju, stratified a, and marginal reliability). Models with different underlying assumptions concerning test-part similarity are discussed. A detailed computational example is presented for the targeted…

Robustness of the school-level item response theoretic (IRT) model to violations of distributional assumptions was studied in a computer simulation. In situations where school-level precision might be acceptable for real school comparisons, expected a posteriori estimates of school ability were robust over a range of violations and conditions.…

Estimation/smoothing methods that are flexible enough to fit a wide variety of test score distributions are reviewed: kernel method, strong true-score model-based method, and method that uses polynomial log-linear models. Applications of these methods include describing/comparing test score distributions, estimating norms, and estimating…

A logistic regression model for characterizing differential item functioning (DIF) between two groups is presented. A distinction is drawn between uniform and nonuniform DIF in terms of model parameters. A statistic for testing the hypotheses of no DIF is developed, and simulation studies compare it with the Mantel-Haenszel procedure. (Author/TJH)

Equal percentile (EP) and partial credit (PC) equatings for raw scores from performance-based assessments with free-response items are compared through the use of data from the Maryland School Performance Assessment Program. Results suggest that EP and PC methods do not give equivalent results when distributions are markedly skewed. (SLD)

A study of the relationship between first-year results for 115 Dutch medical students and achievement during medical school was studied using an item-response theory model for the longitudinal measure of change with stochastic parameters (developed by Albers et al., 1989) indicates that a low rate of growth in the first year persists. (SLD)