[R] irt model estimation with constrained parameters

Fischer, Felix Felix.Fischer at charite.de
Fri May 10 12:59:51 CEST 2013


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

Tel: 030 450 529 104
Fax: 030 450 529 902

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