Item Information and Discrimination Functions for Trinary PCM Items
- 1 December 1997
- journal article
- Published by Cambridge University Press (CUP) in Psychometrika
- Vol. 62 (4) , 569-578
- https://doi.org/10.1007/bf02294643
Abstract
For trinary partial credit items the shape of the item information and the item discrimination function is examined in relation to the item parameters. In particular, it is shown that these functions are unimodal if δ2 − δ1 < 4 ln 2 and bimodal otherwise The locations and values of the maxima are derived. Furthermore, it is demonstrated that the value of the maximum is decreasing in δ2 − δ1. Consequently, the maximum of a unimodal item information function is always larger than the maximum of a bimodal one, and similarly for the item discrimination function.Keywords
This publication has 7 references indexed in Scilit:
- Decomposition of a Rasch Partial Credit Item into Independent Binary and Indecomposable Trinary ItemsPsychometrika, 1996
- On Equivalence between a Partial Credit Item and a Set of Independent Rasch Binary ItemsPsychometrika, 1994
- Information Functions of the Generalized Partial Credit ModelApplied Psychological Measurement, 1993
- A Generalized Partial Credit Model: Application of an EM AlgorithmApplied Psychological Measurement, 1992
- A Rasch Model for Partial Credit ScoringPsychometrika, 1982
- An Extension of the Rasch Model for Ratings Providing Both Location and Dispersion ParametersPsychometrika, 1982
- A Rating Formulation for Ordered Response CategoriesPsychometrika, 1978