The supported IRT (Item Response Theory) model are the Rasch model, the 2PLM (two parameter logistic model) and the 3PLM (three parameter logistic model). The multivariate logistic model and non parametric methods are also supported.
The estimations methods available are the MMLE (Marginal Maximum Likelihood Estimator) and the BME (Bayes Modal Estimator) for the parametric estimation of items, the PMMLE (Penalized MMLE) and kernel smoothing for the non parametric estimation of items, and the ML (Maximum Likelihood) and the EAP (Expected A Posteriori) estimators for the abilities.
Two command line programs called "irt" and "mirt" are also provided.
Ramsay, J.O. (1991). Kernel smoothing approaches to nonparametric item characteristic curve estimation. Biometrika, 56, 611-630.
Rossi, N., Wang, X. & Ramsay, J.O. (2002). Nonparametric item response function estimates with the EM algorithm. Journal of Educational and Behavioral Statistics, 27, 291-317.