Once unidimensionality of criteria is established through EFA, we can fit IRT models to estimate parameters (severity and discrimination) for the craving criterion in the context of existing abuse/dependence criteria, and evaluate the total information provided by the set of criteria in reference to the alcohol use disorder continuum. We fit a 2-parameter logistic IRT model (Birnbaum, 1968) using a maximum likelihood estimator once unidimensionality of the underlying factor structure was established. In MPLUS, 2-parameter IRT models are fit as Confirmatory Factor Analysis (CFA) models, where the CFA model parameters are rescaled to an IRT metric (Bock et al., 1988).
