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Comparing the Effectiveness of Procedures to Detect Item Parameter Drift DIF IRT

Donoghue, John R.; Isham, Steven P.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Differential Item Functioning (DIF), Item Parameters, Item Response Theory (IRT), Monte Carlo Methods, Test Items


This study used Monte Carlo methods to examine the use of several methods to identify item parameter drift. Number of examinees, number of items, and number of drift items in the test were manipulated. Overall, Lord's 2 measure was the most effective in identifying items that exhibited drift. However, the measure was only accurate when the c-parameter was constrained to be equal across calibrations. Of the remaining methods, the best (z-test based on Raju's exact unsigned integral, the PARSCALE computer program's 2 by subgroup, and Kim and Cohen's closed interval signed area measure) required empirical estimates of critical values for the test statistics in order to function well. This aspect detracts from their usefulness.

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