Investigation of Placement Test in terms of Item Biasness

Abstract

This study was conducted to analyze the Centralized High School Entrance placement test (SBS) in terms of item biasness. In this research, it is examined that whether Turkish, Science and Technology, Math and Social Sciences sub-tests items in 8th grade placement test (SBS) applied in 2009 to study the biasness in terms of gender and school type. This research was conducted on randomly selected 7000 students from public schools, 1000 students from private schools and 1000 students from regional boarding primary education schools (YIBOs). The placement test (SBS) consists of Turkish, Math, Science and Technology, Social Sciences and Foreign Language subtests. In this study, the data of Foreign Language subtest wasn’t used. Turkish subtest consists of 23 items; Math, Science and Technology and Social Sciences subtests consists of 20 items each. To check whether the data prove the unidimensionality assumption, the factor analysis is applied to the items constructed in the subtests. At the end of the factor analysis, DIF analysis was maintained for 18 items in Turkish subtest, 14 items in Math subtest, 14 items in Science and Technology subtest and 18 items in Social Sciences subtest (64 items in total). It was investigated whether there is DIF in the items of subtests or not with Mantel-Haenszel, SIBTEST and logistic regression methods. Items showing DIF according to at least two of these methods are handled as biased items and the reasons of biasness in these items are examined by taking experts’ opinions. All but 4 of items showing DIF were biased by experts. According to experts items may show bias because of the group properties and items. Experts could not give common and consistent explanations for three items in the Math subtest and one item of Turkish subtest showing DIF. It was concluded that resulting DIF in these items is not due to bias.