How to Treat Omitted Responses in Rasch Model-Based Equating

This study investigated the impact of the coding scheme on IRT-based true score equating under a common-item nonequivalent groups design. Two different coding schemes under investigation were carried out by assigning either a zero or a blank to a missing item response in the equating data. The inves...

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Bibliographic Details
Published in:Practical assessment, research & evaluation research & evaluation, 2009-01, Vol.14 (1), p.1
Main Author: Shin, Seon-Hi
Format: Article
Language:English
Subjects:
Coding
Comparative Analysis
Equated Scores
Item Response Theory
Monte Carlo Methods
Omitted Responses
Rasch model
Sample Size
True Scores
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Summary:This study investigated the impact of the coding scheme on IRT-based true score equating under a common-item nonequivalent groups design. Two different coding schemes under investigation were carried out by assigning either a zero or a blank to a missing item response in the equating data. The investigation involved a comparison study using actual large scale data and then Monte Carlo simulations for a systematic inspection on the topic. The recommendations on the basis of the findings of the study were made to treat omitted responses as not-administered rather than as wrong, and use a large sample size to ensure the accuracy of the screening tools such as the displacement index and the robust-"z" statistic during equating. (Contains 4 figures and 1 table.)
ISSN:1531-7714
1531-7714