hi,
is there a way to estimate the parameters of an IRT model (in my case, the graded response model), when some item parameter are already known? what i have heard is that other irt programs such as parscale allow to prespecify some of the item difficulty and location parameters and estimate only the unconstrained parameters.
i usually use ltm for model estimation.
best, felix
Dr. rer. nat. Felix Fischer
Diplom-Psychologe
Institut f?r Sozialmedizin, Epidemiologie und Gesundheits?konomie
Charit? - Universit?tsmedizin Berlin
Luisenstrasse 57
10117 Berlin
Tel: 030 450 529 104
Fax: 030 450 529 902
http://epidemiologie.charite.de