In IRT research, the Gibbs sampler is used in two versions: a version with a normal ogive representation such as in Eq. 1, introduced by Albert (1992), and a version with a logistic representation introduced by Patz and Junker (1999a). Below, a logistic version will be used for simulated and real data, implemented in the freely obtainable MCMC software package WinBUGS (http://www.mrc-bsu.cam.ac.uk/bugs/).
