Generalising IRT to Discriminate Between Examinees

We present a generalisation of the IRT framework that allowsto discriminate between examinees. Our model thereforeintroduces examinee parameters that can be optimisedwith Expectation Maximisation-like algorithms. We provideempirical results on PISA data showing that our approachleads to a more appropriate grouping of PISA countries thanby test scores and socio-economic indicators.