Identifying the Differential item functioning Sources in I.R.I. Police Employment Test Using Item-Focused Tree Model

The purpose of the present study is to identify the differential item functioning sources of the questions in the police command employment test in 2022 using the item-focused tree model.
In terms of its objectives the current research is of applied research type and in terms of method it is a descriptive study. Also, due to the fact that this research examines employment tests, in terms of method, it is of evaluation type. The statistical population included all 2000 participants in the employment test of police command in 2022. However, due to the existence of missing data (i.e. cases where the candidates did not answer the test questions), the sample size of the valid data set included 1098 individuals that was used as the basis of the analysis. DIFtree package in R software was used to analyze the data and reveal the differential item functioning of the question using the item-focused tree model.
The findings showed that 6 items in the uniform mode and 6 items in the non-uniform mode have a differential functioning. In the uniform mode, items 20 and 89 with regard to the age variable and items 21, 23, 52 and 74 with regard to the academic field variable have a differential functioning. In the uniform mode, the variables do not interact in inducing differential functioning. In the non-uniform condition, in item 27, both age and field of study variables interact differently, and in items 13, 34, 49, and 55, according to the field of study variable and item 92, according to the age variable, have a different functioning.
The item-focused tree model on the question based on the logistic regression has been able to show the existence of direction in the test questions and this can promise to improve the methodology of the employment tests.