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Polytomous item response theory parameter recovery: An investigation of non-normal distributions and small sample size Open Access


Other title
Item Response Theory
Parameter Recovery
Graded Response Model
Type of item
Degree grantor
University of Alberta
Author or creator
Bahry, Louise M
Supervisor and department
Rogers, W. Todd (Educational Psychology)
Examining committee member and department
Cui, Ying (Educational Psychology)
Varnhagan, Connie (Psychology)
Department of Educational Psychology
Measurement, Evaluation and Cognition
Date accepted
Graduation date
Master of Education
Degree level
Item Response Theory (IRT) has been extensively used in educational research with large sample sizes and normally distributed traits. However, there are cases in which distributions are not normal, and research has shown that the estimation of parameters becomes problematic with non-normal data. This study investigates the effects of skewness on parameter estimation using the Graded Response Model (GRM) and MULTILOG. Three distribution types (extreme and moderate skewness and a baseline condition (i.e. normal) and seven sample sizes (from n = 100 to n = 3,000) were investigated using simulations. In keeping with previous findings, the extremely skewed distribution condition resulted in the poorest estimates regardless of sample size. In general, the accuracy of parameter estimation increased as sample size increased. For the normally distributed conditions, results suggest a minimum sample size of 750 for accurate estimation. Implications of these findings are discussed.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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