NCJ Number
91854
Journal
Psychometrika Volume: 47 Issue: 2 Dated: (June 1982) Pages: 149-174
Date Published
1982
Length
26 pages
Annotation
A unidimensional latent trait model for responses scored in two or more ordered categories is developed. This 'Partial Credit' model is a member of the family of latent trait models which share the property of parameter separability and so permit 'specifically objective' comparisons of persons and items.
Abstract
The model can be viewed as an extension of Andrich's Rating Scale model to situations in which ordered response alternatives are free to vary in number and structure from item to item. The paper demonstrates the difference between the parameters in this model and the 'category boundaries' in Samejima's Graded Response model. It develops an unconditional maximum likelihood procedure for estimating the model parameters. Figures, tables, equations, 4 notes, and 22 references are included. (Author abstract modified)