Measurement has been ubiquitous in all areas of education for at least a century. Various methods have been suggested to examine the fairness of education tests especially in high-stakes contexts. The present study has adopted the newly proposed ecological approach to differential item functioning (DIF) to investigate the fairness of the Iranian nationwide university entrance exam. To this end, the actual data from an administration of the test were obtained and analyzed through both traditional logistic regression and latent class analysis (LCA) techniques. The initial DIF analysis through logistic regression revealed that 19 items (out of 70) showed either uniform or non-uniform DIF. Further examination of the sample through LCA showed that the sample is not homogeneous. LCA class enumeration revealed that three classes can be identified in the sample. DIF analysis for separate latent classes showed that three serious differences in the number of DIF items identified in each latent class ranging from zero items in latent class 3 to 43 items in latent class 2. The inclusion of the covariates in the model also showed that latent class membership could be significantly predicted from high school GPA, field of study, and acceptance quota. It is argued that the fairness of the test might be under question. The implications of the findings for the validity of the test are discussed in detail.
