Accuracy of three exact person tests for assessing model-data fit in the Rasch model was investigated in a simulation study. Empirical Type I error rates and statistical power of the person tests were computed. The exact person test conditioned on total score is a promising tool for assessing consistency of response patterns with the Rasch model.…

This study examined the application of the marginal maximum likelihood-EM algorithm to the parameter estimation problems of the normal ogive and logistic polytomous response models for Likert-type items. A rating scale model, based on F. Samejima's (1969) graded response model, was developed. (TJH)

A two-stage process that considers the multidimensionality of tests under the framework of unidimensional item response theory is described and evaluated. Findings from a simulation indicate that gains in estimation robustness and score interpretation are possible with almost no sacrifice of goodness of fit when using this two-stage approach. (SLD)