Testfact is one of the mostly used software products in the field of Item Response Theory. Together with BILOG MG, Parscale and Multilog, you have an excellent suite of IRT products.

Testfact features

- Marginal maximum likelihood (MML) exploratory factor analysis and classical item analysis of binary data
- Computes tetrachoric correlations, principal factor solution, classical item descriptive statistics, fractile tables and plots
- Handles up to 10 factors using numerical quadrature: up to 5 for non-adaptive and up to 10 for adaptive quadrature
- Handles up to 15 factors using Monte Carlo integration techniques
- Varimax (orthogonal) and PROMAX (oblique) rotation of factor loadings
- Handles an important form of confirmatory factor analysis known as "bifactor" analysis: Factor pattern consists of one main factor plus group factors
- Simulation of responses to items based on user specified parameters
- Correction for guessing and not-reached items
- Allows imposition of constraints on item parameter estimates
- Handles omitted and not-presented items
- Detailed online HELP documentation includes syntax and annotated examples.