Type I error rates were examined for several fit indices available in GGUM2000: extensions of Infit, Outfit, Andrich's X(2), and the log-likelihood ratio X(2). Infit and Outfit had Type I error rates much lower than nominal alpha. Andrich's X(2) had Type I error rates much higher than nominal alpha, particularly for shorter tests or larger sample…

A probabilistic item response theory (IRT) model is developed for pair-comparison design in which the unfolding principle governing the choice process uses a discriminant process analogous to Thurstone's Law of Comparative Judgment. A simulation study demonstrates the feasibility of estimation, and two examples illustrate the implications for…