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Abstract

This study aimed to examine the validity and reliability of the Bebras test, which was cross-culturally adapted and adjusted to fit the Thai context. Both Classical Test Theory (CTT) and Modern Test Theory (MTT) were employed to analyze the data. The sample comprised of 115 grade 9 students. The research instrument was the Bebras test, a standardized assessment developed by Vilnius University in Lithuania. Data analysis employed CTT, yielding an average difficulty index of 0.57 and an average discrimination index of 0.42. Additionally, the Rasch model was applied to assess the students’ abilities and item difficulties. The findings revealed that the median student ability and item difficulty were closely aligned, indicating that the test was well-suited to the students’ ability levels. The weighted likelihood estimation reliability (WLE Reliability) was 0.659, with infit and outfit values falling within an acceptable range, demonstrating high validity. The ability levels ranged from -2.5 to 3.5 logits, and the fit indices were consistent with empirical data. Furthermore, the distribution of item difficulty and student ability, as illustrated by the Wright map, suggested that the test could effectively assess students with a wide range of abilities. Based on these findings, the study recommends that if the test is to be used with students from other educational settings, a preliminary pilot test should be conducted to evaluate whether the test is suitable for those students and to adjust test that is better aligned with their ability levels.

Publisher

Faculty of Education, Chulalongkorn University

DOI

10.14456/jescu.2025.21

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