Gender-Related Differential Item Functioning in Vocational Interest Measurement An Analysis of the AIST-R

Large mean differences are consistently found in the vocational interests of men and women. These differences may be attributable to real differences in the underlying traits. However, they may also depend on the properties of the instrument being used. It is conceivable that, in addition to the intended dimension, items assess a second dimension that differentially influences responses by men and women. This question is addressed in the present study by analyzing a widely used German interest inventory (Allgemeiner Interessen-Struktur-Test, AIST-R) regarding differential item functioning (DIF) using a DIE estimate in the framework of item response theory. Furthermore, the impact of DIF at the scale level is investigated using differential test functioning (DTF) analyses. Several items on the AIST-R's scales showed significant DIF, especially on the Realistic, Social, and Enterprising scales. Removal of DIF items reduced gender differences on the Realistic scale, though gender differences on the Investigative, Artistic, and Social scales remained practically unchanged. Thus, responses to some AIST-R items appear to be influenced by a secondary dimension apart from the interest domain the items were intended to measure.