eRm-package: extended Rasch modeling
Description
This package estimates extended Rasch models, i.e. the
ordinary Rasch model for dichotomous data (RM), the linear logistic test model (LLTM),
the rating scale model (RSM) and its linear extension (LRSM), the partial credit model (PCM)
and its linear extension (LPCM). The parameters are estimated by conditional maximum likelihood (CML).Details
ll{
Package: eRm
Type: Package
Version: 0.3.1
Date: 2006-10-06
License: GPL2 or higher
}
The basic input units for the functions are the person-item-matrix X and the design matrix W.
By default, W is generated automatically, but it can be specified by the user as well. The function
call of the basic models is RM(X, W), RSM(X, W), and PCM(X, W).
The linear extensions provide the possibility to fit a more restricted model than its basic complement, but
also a generalization by imposing repeated measurement designs and group contrasts. These models can
be estimated by using e.g. the call LLTM(X, W, mpoints = 2, groupvec = G), LRSM(X, W, mpoints = 2, groupvec = G), and
LPCM(X, W, mpoints = 2, groupvec = G). G is a vector with the group membership of each subject.References
Fischer, G. H., and Molenaar, I. (1995). Rasch Models - Foundations,
Recent Developements, and Applications. Springer.