Randomization tests are often recommended when parametric assumptions may be violated because they require no distributional or random sampling assumptions in order to be valid. In addition to being exact, a randomization test may also be more powerful than its parametric counterpart. This was demonstrated in a simulation study which examined the…

Test of homogeneity of covariances (or homoscedasticity) among several groups has many applications in statistical analysis. In the context of incomplete data analysis, tests of homoscedasticity among groups of cases with identical missing data patterns have been proposed to test whether data are missing completely at random (MCAR). These tests of…

A similarity-based smoothing approach to nondimensional item analysis was studied. Simulated and actual data are presented to show that when responses are determined by a latent ability variable, this similarity-based smoothing procedure can reveal the dimensionality of ability satisfactorily. (SLD)

The Individual Scaling with Individual Subjects (ISIS) procedure appears to be a viable implementation of an incomplete design for collecting real as well as simulated data. Applied to a multidimensional set of data, it reduced the number of judgments required by more than half and yet gave the same number of dimensions. (Author/RC)

A method is developed for estimating the response time distribution of an unobserved component in a two-component serial model. The estimate of the component's density function is constrained to be only unimodal and non-negative. Numerical examples suggest the method can yield reasonably accurate estimates with sample sizes of 300. (Author/CTM)

Studied the use of the person response function (PRF) for identifying nonfitting item score patterns. Proposed a person-fit method reformulated in a nonparametric item response theory (IRT) context. Conducted a simulation study to compare the use of the PRF with a person-fit statistic, resulting in the conclusion that the PRF can be used as a…

Unlike their monotone counterparts, nonparametric unfolding response models, which assume the item response function is unimodal, have seen little attention in the psychometric literature. This paper studies the nonparametric behavior of unfolding models by building on the work of Post (1992). The paper provides rigorous justification for a class…

Nonparametric item response models have been developed as alternatives to the relatively inflexible parametric item response models. An open question is whether it is possible and practical to administer computerized adaptive testing with nonparametric models. This paper explores the possibility of computerized adaptive testing when using…