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ERIC Number: ED442839
Record Type: Non-Journal
Publication Date: 2000-Apr
Pages: 58
Abstractor: N/A
Reference Count: N/A
The Effect of Unequal Variances in the Ability Distributions on the Type I Error Rate of the Mantel-Haenszel Chi-Square Test for Detecting DIF.
Monahan, Patrick
Previous studies that investigated the effect of unequal ability distributions on the Type I error (TIE) of the Mantel-Haenszel chi-square test for detecting differential item functioning (DIF) simulated ability distributions that differed only in means. This simulation study suggests that the magnitude of TIE inflation is increased, and the type of items that show inflation are somewhat broadened, under the realistic scenarios of ability distributions that differ not only in means but also in variances or variances alone. There were several conditions for which unequal variances in the ability distributions, either alone, or in combination with unequal means, produced practically important TWI inflation when no such inflation was observed under unequal means alone. This occurred primarily for the hard and medium difficulty items with high discrimination and on the short test with the total sample size of 2,000, but it was also observed for the medium-length test. The most peculiar finding was the aberrant behavior of the highly discriminating hard items, which was the only item to show marked TIE inflation due to unequal variances alone when only rare mild inflation was observed under the combination of unequal variances and unequal means. (Contains 14 tables, 5 figures, and 39 references.) (SLD)
Publication Type: Reports - Evaluative; Speeches/Meeting Papers
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A