The articles in this special issue of the "Journal of Applied Testing Technology" represent significant steps forward in the area of evaluating the validity of methods for assessing the educational achievement of students with disabilities. The studies address some of the most difficult student groups to assess--students with learning…

Multidimensional scaling (MDS) is a versatile technique for understanding the structure of multivariate data. Recent studies have applied MDS to the problem of evaluating content validity. This paper describes the importance of evaluating test content and the logic of using MDS to analyze data gathered from subject matter experts employed in…

Describes content-validity theory and illustrates new and traditional approaches for conducting content-validity studies. Newer approaches are based on multidimensional scaling analysis of item-similarity ratings, while traditional approaches are based on ratings of item-objective congruence and relevance. (Author/SLD)

Whether item response theory (IRT) is useful to the small-scale testing practitioner is examined. The stability of IRT item parameters is evaluated with respect to the classical item parameters (i.e., p-values, biserials) obtained from the same data set. Previous research investigating the effect of sample size on IRT parameter estimation has…