Validation of an assessment instrument - SCALE using Rasch analysis: A brief report

This study aims to report on the psychometric properties of SCALE, a newly developed assessment instrument, that is based on the central curriculum for students with intellectual disabilities, using Rasch Analysis. Results indicated that the SCALE could classify students into at least 13 levels of abilities, and that the range of item difficulty was capable of stratifying students’ abilities into 8 to 11 attainment levels. The Rasch statistics demonstrated that the assessment results using SCALE had a high degree of validity and reliability. Its uni-dimensionality as an instrument to measure the attainment levels of the four Key Learning Areas in the central curriculum was also supported. Results from the Rasch Analysis showed that the SCALE measure is a well-validated instrument in identifying the differential levels of attainment. Based on the SCALE data, teachers can design learning materials and activities to match the performance levels of individual students. In addition, the use of the SCALE attainment descriptors to differentiate students’ attainment levels would enable teachers in schools to document progress of their students within an academic year. Subsequently, this enable them to reflect on their teaching effectiveness and make adjustments for the following year. Copyright © 2014 The Hong Kong Institute of Education : Special Education Society of Hong Kong.