Identifying Negatively Discriminating Items When Test Scores are Not Normally Distributed

Traditional item analysis procedures for norm referenced testing have often included the selection of the upper and lower 27% groups for performing item discriminations. Such procedures are based upon assumptions of (a) normality, (b) score independence in the tails, and (c) equality of standard dev...

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Bibliographic Details
Published in:Educational and psychological measurement 1992-03, Vol.52 (1), p.31-39
Main Authors: Fowler, Robert L., Clingman, Joy M.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Classroom Techniques
Elementary Secondary Education
Equations (Mathematics)
Fundamental and applied biological sciences. Psychology
Item Analysis
Item Bias
Item Discrimination (Tests)
Mathematical Models
Monte Carlo Methods
Nonnormal Distributions
Objective Tests
Population Parameters
Power (Statistics)
Psychology. Psychoanalysis. Psychiatry
Psychology. Psychophysiology
Psychometrics. Statistics. Methodology
Schools
Scores
Statistical Distributions
Statistics
Statistics. Mathematics
Test Items
Tests
Citations: Items that this one cites
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Summary:Traditional item analysis procedures for norm referenced testing have often included the selection of the upper and lower 27% groups for performing item discriminations. Such procedures are based upon assumptions of (a) normality, (b) score independence in the tails, and (c) equality of standard deviations in the tails of the criterion distribution. However, these characteristics may not apply to the distributions of typical classroom examinations, which tend to be negatively skewed. This study used Monte Carlo techniques to examine the power of Brennan's (1972) B to detect negatively discriminating items drawn from a variety of nonnormal population distributions. In general, it was found that power is lost when choosing equal-sized groups from asymmetric distributions. A simplified procedure for conducting an item discrimination analysis on typical classroom objective examinations is offered.
ISSN:0013-1644
1552-3888
DOI:10.1177/001316449205200103