An information-correction method for testlet-based tests is introduced. This method takes advantage of both generalizability theory (GT) and item response theory (IRT). The measurement error for the examinee proficiency parameter is often underestimated when a unidimensional conditional-independence IRT model is specified for a testlet dataset. By…

Item response theory (IRT) methodology is introduced as a tool for improving assessment instruments used with people who have disabilities. Need for this approach in rehabilitation is emphasized; differences between IRT and classical test theory are clarified. Concepts essential to understanding IRT are defined, necessary data assumptions are…

Three item selection methods for criterion-referenced tests are examined: the classical theory of item difficulty and item-test correlation; the latent trait theory of item characteristic curves; and a decision-theoretic approach for optimal item selection. Item contribution to the standardized expected utility of mastery testing is discussed. (CM)