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Linking Parameters Estimated With the Generalized Graded Unfolding Model: A Comparison of the Accuracy of Characteristic Curve Methods

National Research Council, jkoenig{at}nas.edu

James S. Roberts

Georgia Institute of Technology

Methods for linking item response theory (IRT) parameters are developed for attitude questionnaire responses calibrated with the generalized graded unfolding model (GGUM). One class of IRT linking methods derives the linking coefficients by comparing characteristic curves, and three of these methods—test characteristic curve (TCC), item characteristic curve (ICC), and operating characteristic curve (OCC)—are extended for use with the GGUM. Alternate versions of these methods are developed to produce both symmetric and asymmetric solutions. The adequacy of these methods for use with the GGUM is evaluated in a simulation that varied the distributions of in the groups to be linked and the number of individuals and anchor items used for linking. All methods performed well under the conditions studied. Statistically significant effects were found for sample size and number of anchor items. It is recommended that choice of linking method should consider the context and intent of the linking.

Key Words: Index terms: item response theory • generalized graded unfolding models • GGUM • linking • attitude questionnaires • characteristic curve methods

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