The Consistency of DIF/DTF across Different Test Administrations: A Multidimensional Perspective.

This study was patterned after a previous study by Skaggs and Lissitz (1992) in which inconsistency of differential item functioning (DIF) was reported across test administrations. They suggested multidimensionality of test data as one possible reason for inconsistency. Therefore, in this study, DIF indices which were developed recently with a multidimensional perspective were included. In addition, the consistency of differential test functioning (DTF) was evaluated. DIF/DTF analyses were conducted for both gender and ethnic differences. Ten random samples of 1,000 examinees from each gender and ethnic category were taken from a math basic skills test which was administered in a statewide testing program in two separate years (1984 and 1987). In general, results indicated a more favorable evaluation of the consistency of DIF indices than the Skaggs and Lissitz study. Possible reasons for conflicting conclusions are discussed. (Contains 18 references and 9 tables.) (Author/SLD)