Validation of a science concept inventory by rasch analysis

Abstract

The purpose of this study was to describe the Rasch analysis of a newly developed 22-item science concept instrument, which was administered to grade 7 students (N = 2163) across a large sample of classrooms (N = 115) in secondary schools (N = 16) in Singapore. In view of the broad domain-specificity of science education, and in consideration of students’ prior knowledge, the topic of cell system was identified as a suitable theme for the concept test. First, we used item analysis to investigate the psychometric properties and adequacy of the test items, following which we proceeded to assess the overall fit of the test to the Rasch model. Results indicate that the instrument is reasonably robust with respect to the Rasch model. Differential item functioning was investigated with respect to gender and academic track, and relationships with external related variables (e.g., prior attainment, science self-efficacy) were also examined. Implications are discussed in light of the findings, with recommendations for areas for improvement.