LINKING MULTIDIMENSIONAL ITEM CALIBRATIONS

Invariance of trait scales across changing samples of items and examin ees is a central tenet of item response theory (IRT). However, scales defined by most IRT models are truly invariant with respect to certain linear transformations of the parameters, The problem is to find the proper transformation that places separate calibrations on a common sc ale. A variety of procedures for estimating transformations have been proposed for unidimensional models. This paper explores some issues in volved in extending and adapting unidimensional linking procedures for use with multidimensional IRT models.