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Simulated Tests of Differential Item Functioning Using SIBTEST With and Without Impact
Author(s) -
Klockars Alan J.,
Lee Yoonsun
Publication year - 2008
Publication title -
journal of educational measurement
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.917
H-Index - 47
eISSN - 1745-3984
pISSN - 0022-0655
DOI - 10.1111/j.1745-3984.2008.00064.x
Subject(s) - differential item functioning , statistics , type i and type ii errors , monte carlo method , sample size determination , statistical power , null hypothesis , mathematics , psychology , masking (illustration) , item response theory , audiology , psychometrics , medicine , art , visual arts
Monte Carlo simulations with 20,000 replications are reported to estimate the probability of rejecting the null hypothesis regarding DIF using SIBTEST when there is DIF present and/or when impact is present due to differences on the primary dimension to be measured. Sample sizes are varied from 250 to 2000 and test lengths from 10 to 40 items. Results generally support previous findings for Type I error rates and power. Impact is inversely related to test length. The combination of DIF and impact, with the focal group having lower ability on both the primary and secondary dimensions, results in impact partially masking DIF so that items biased toward the reference group are less likely to be detected.