USING STATISTICAL POWER ANALYSIS FOR IDENTIFYING DIFFERENTIAL ITEM FUNCTIONING IN TWO TEST FORMATS
Abdul-Wahab Ibrahim · FUDMA Journal of Educational Foundations · 2019
The relative power of three statistical techniques for identifying Differential Item Functioning in dichotomous and ordinal test formats was investigated. The study adopted a descriptive-comparative research design. Data on an intact class of 513 Part 3 undergraduate students were obtained from 2 alternative test formats of 50 and 25 items each respectively. Two research instruments were used to collect data. Data collected were analyzed using Generalized Mantel-Haenszel, Simultaneous Item Bias Test, and Logistic Discriminate Function Analysis. The results showed that there was no significant relationship between the proportions of test items that function differentially in the dichotomous and ordinal tests when the different methods are used. Further, the three statistical methods complement each other in their ability to detect DIF in the dichotomous and ordinal test formats as all of them have capacity to detect DIF but perform differently. The study concluded that there was a high degree of correspondence between the three procedures in their ability to detect DIF in dichotomous and ordinal tests. It was recommended that test experts and developers should consider using statistical approaches in DIF detection