Differential Item Functioning on the Armed Services Vocational Aptitude Battery
Gibson, Shanan Gwaltney IV
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Utilizing Item Response Theory (IRT) methodologies, the Armed Services Vocational Aptitude Battery (ASVAB) was examined for differential item functioning (DIF) on the basis of crossed gender and ethnicity variables. Both the Mantel-Haenszel procedure and an IRT area-based technique were utilized to assess the degree of uniform and non-uniform DIF in a sample of ASVAB takers. The analysis was performed such that each subgroup of interest functioned as the focal group to be compared to the male reference group. This type of DIF analysis allowed for comparisons within ethnic group, within gender group, as well as crossed ethnic/gender group. The groups analyzed were: White, Black, and Hispanic males, and White and Black females. It was hypothesized that DIF would be found, at the scale level, on several of the ASVAB sub-tests as a result of unintended latent trait demands of items. In particular, those tests comprised of items requiring specialized jargon, visuospatial ability, or advanced English vocabulary are anticipated to show bias toward white males and/or white females. Findings were mixed. At the item level, DIF fluctuated greatly. Numerous instances of DIF favoring the reference as well as the focal group were found. At the scale level, inconsistencies existed across the forms and versions. Tests varied in their tendency to be biased against the focal group of interest and at times, performed contrary to expectations.
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