A Partial Test of Hulin's Psychometric Theory of Measurement Equivalence in Translated Tests

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Abstract
Hulin (1987) suggested that the a and b parameters of item characteristic curves (ICCs) for test items that function differentially when translated for use in another culture (i.e., DIF items) may provide useful information about the source of DIF. Hulin hypothesized that a-parameter differences and b-parameter differences “have much different linguistic and measurement implications.” He proposed that DIF due to b-parameter differences is due to translation error; DIF due to a-parameter differences is indicative of more “profound cultural bias.” The 118-item Trier Personality Inventory was administered (in German) shortly after reunification to 300 East and 298 West Germans. Thus, the source of any DIF discovered could not be due to translation error. IRT analysis revealed two significant DIF items and two items with DIF indices that approached significance. In disagreement with Hulin, there were large differences in the b parameters along with modest differences in the a parameters for three out of four DIF items. Likewise, examination of ICCs for DIF items failed to provide empirical support for Hulin's hypothesis. Implications of these findings for test translators are discussed.