Investigation of differential item functioning of the PISA 2015 science literacy items with the latent class approach

Authors : Onurcan Ceyhan, Hamide Deniz Gülleroğlu
Pages : 178-204
Doi:10.33400/kuje.1158799
View : 44 | Download : 56
Publication Date : 2025-05-31
Article Type : Research Paper
Abstract :This study examines 11 items determined among the science literacy items of the PISA 2015 in terms of DIF using the latent class method. In the initial investigations, the response pattern met the assumptions of unidimensionality, monotony and local independence, which are the assumptions of the IRT for Türkiye study group consisting of 506 people. As a result of the estimations made with the IRT, it was concluded that items were suitable for the Mixed IRT 2PLM with two latent classes. The analyses were conducted based on the Mixed IRT 2PLM with two latent classes, and it was determined that approximately 91% of the respondents were in the first and 9% were in the second latent class. In the DIF analysis based on the Mixed IRT 2PLM with two latent classes, item 4 showed both non-uniform and uniform DIF. It was concluded that the items numbered 5, 6, 9, and 11 only showed uniform DIF. Item 4, 5, 6, 9, and 11 functioned differently in two latent classes. In the literature review, variables reported as DIF sources were included in the model separately as covariant variables. The percentage of classification accuracy increased among these covariant variables such as gender, ICT resources, enjoyment of science, and sense of belonging to the school. Therefore, these specified covariant variables serve as either a predictor of the latent variable or a source of a priori knowledge. Observed variables were added as covariant variables, DIF was determined as a source, and it was concluded that they were insufficient to explain latent classes. This study showed that if the DIF source based on the observed variable had a weak relationship with the latent variable, it did not significantly affect the validity of the test results.
Keywords : PISA, değişen madde fonksiyonu, gizil sınıf yaklaşımı, kovaryant, karma madde tepki kuramı

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