Examination of Gender-Related Differential Item Functioning Through Poly-BW Indices

The existing differential item functioning (DIF) detection approaches relying on item difficulty or item discrimination are limited for understanding the associates of DIF items, and consequently, DIF items were conventionally either deleted or ignored. Given the importance of minimizing DIF items in test construction, teachers or testing practitioners need more information regarding possible associates of DIF items. Using an example of a teacher-made mathematics achievement test, this study aimed to examine how the Poly-BW indices (power, defenselessness, disturbance, and hint) contributed to the properties of gender-related DIF items. Data from a 34-item mathematics achievement test that involved 1,439 seventh-grade students from Taiwan (51.01% boys and 48.99% girls) showed that the differences of the defenselessness (mp) and power (cp) indices between men and women served as salient predictors of the DIF measures estimated by the Poly Simultaneous Item Bias Test (Poly-SIBTEST) procedure and with satisfactory accuracy of hit rates. Items with relatively large defenselessness for men were likely to present male-favoring DIFs, whereas items with relatively large power for men were likely to present female-favoring DIFs. The Poly-BW indices yielded directions for modifying items for teachers in practice.