An Evaluation of Items and Dimensional Structure of a Scale to Measure Teachers' Professional Commitment in Thailand

The purpose of this study was to examine the items and the dimensionality of a scale to measure professional commitment of teachers in Thailand. Data were collected by in-depth interview and questionnaire. The content analysis was conducted with the qualitative data for the purpose of item writing. Differential item functioning (DIF), exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and bi-factor CFA model analysis were conducted to establish validity evidence. As a result of EFA and CFA, the study showed that a 3-dimensional scale can effectively measure professional commitment of teachers, which was achieved by the 18-item measure. A polytomuos item response theory model was also fitted to estimate item parameters and to examine the test information function.