| Abstract: | An IRT model with a parameter-driven process for change is proposed. Quantitative differences between persons are taken into
account by a continuous latent variable, as in common IRT models. In addition, qualitative interindividual differences and
autodependencies are accounted for by assuming within-subject variability with respect to the parameters of the IRT model.
In particular, the parameters of the IRT model are governed by an unobserved or “hidden'” homogeneous Markov process. The
model includes the mixture linear logistic test model (Mislevy & Verhelst, 1990), the mixture Rasch model (Rost, 1990), and
the Saltus model (Wilson, 1989) as specific instances. The model is applied to a longitudinal experiment on discontinuity
in conservation acquisition (van der Maas, 1993).
Frank Rijmen was supported by the Fund for Scientific Research Flanders (FWO), the GOA/2000/02 granted by the Katholieke Universiteit
Leuven to Paul De Boeck and Iven Van Mechelen, and the PDM/02/067 granted by the Katholieke Universiteit Leuven to Paul De
Boeck. |
