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ERIC Number: EJ1011156
Record Type: Journal
Publication Date: 2013-Jun
Pages: 16
Abstractor: As Provided
ISSN: ISSN-0013-1644
The Langer-Improved Wald Test for DIF Testing with Multiple Groups: Evaluation and Comparison to Two-Group IRT
Woods, Carol M.; Cai, Li; Wang, Mian
Educational and Psychological Measurement, v73 n3 p532-547 Jun 2013
Differential item functioning (DIF) occurs when the probability of responding in a particular category to an item differs for members of different groups who are matched on the construct being measured. The identification of DIF is important for valid measurement. This research evaluates an improved version of Lord's chi [superscript 2] Wald test for comparing item response model parameter estimates between two groups. The improved version uses better approaches for computation of the covariance matrix and equating the item parameters across groups. There are two equating algorithms implemented in IRTPro and flexMIRT software: Wald-1 (one-stage) and Wald-2 (two-stage), only one of which has been studied in simulations before. The present study evaluates for the first time the Wald-1 algorithm and Wald-1 and Wald-2 for three groups simultaneously. A comparison to two-group IRT-LR-DIF is included. Results indicate that Wald-1 performs very well and is recommended, whereas Type I error is extremely inflated for Wald-2. Performance of IRT-LR-DIF and Wald-1 was similar, even for three groups. (Contains 3 tables.)
SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
IES Funded: Yes
Grant or Contract Numbers: R305D100039