The item difficulty should be a property irrespective of a particular population, as well as the ability of a person should be a characteristic without relation to any particular set of items. In this context, the analysis of the differential item functioning (DIF) searches for detecting items whose probability of correctness differs between distinct groups, whose people possess the same level of ability in the variable measured. For the analysis of this question, the types of approaching for its detention and the procedures for DIF identification are mainly argued. Moreover, it is argued that the Rasch model supplies a structure that allows the comparison of the observed results with the predict ones, evaluating the probability of the observed result, equating problems not solved by the other models.
Bias; Rasch Model; Ability; Item