This (unidimensional) dataset includes item parameters for two groups estimated under 
the three parameter logistic model, the generalized partial credit model, and 
the nominal response model. There are 15 common items (7 drm, 3 gpcm, 5 nrm).
This dataset is for illustrative purposes to show how items from different
response models can be mixed together and common items can be in different
positions across groups.

datasets

Item response theory based methods are used to compute
linking constants and conduct chain linking of unidimensional
or multidimensional tests for multiple groups under a common
item design.  The unidimensional methods include the Mean/Mean,
Mean/Sigma, Haebara, and Stocking-Lord methods for dichotomous
(1PL, 2PL and 3PL) and/or polytomous (graded response, partial
credit/generalized partial credit, nominal, and multiple-choice
model) items.  The multidimensional methods include the least
squares method and extensions of the Haebara and Stocking-Lord
method using single or multiple dilation parameters for
multidimensional extensions of all the unidimensional
dichotomous and polytomous item response models.  The package
also includes functions for importing item and/or ability
parameters from common IRT software, conducting IRT true score
and observed score equating, and plotting item response
curves/surfaces, vector plots, information plots, and comparison
plots for examining parameter drift.

Jonathan Weeks

plink

IRT Separate Calibration Linking Methods

dgn function

A list of length four.  The first element is a list of length two with item
parameter estimates for groups 1 and 2 respectively.  The gpcm items do not
include a location parameter.  The second list element is a list identifying 
the number of response categories for the two groups.  The third element, 
specifies which items correspond to the different item response models for each 
group respectively.  The last element is a matrix of common items between the two 
groups.

dgn: Unidimensional Mixed-Format Item Parameters

Description

Usage

Arguments

Format

References