[R] irt model estimation with constrained parameters

[Fischer, Felix]

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 für Sozialmedizin, Epidemiologie und Gesundheitsökonomie
Charité - Universitätsmedizin Berlin
Luisenstrasse 57
10117 Berlin

Tel: 030 450 529 104
Fax: 030 450 529 902
http://epidemiologie.charite.de