Item response curve analysis of Likert scale on learning attitudes towards physics

Abstract The item response curve (IRC) shows the proportion of item responses plotted against total scores achieved in an assessment instrument. It has acquired widespread employment in the field of physics education to analyze tests on physics content knowledge. In the current study, the IRC was lengthened to investigate attitude items of Colorado Learning Attitudes about Science Survey (CLASS) with a five-point Likert rating format. How well the IRC explained polytomous data and its advantages were considered. Collected data were from 1069 engineering undergraduates at a Thai university. The study focused on 16-item CLASS in component 1 pertaining to personal application and relation to the real world, which conformed to item response theory (IRT) assumptions. It revealed robust positive linear relationships of step parameters and difficulty indices derived between IRC and Rasch analysis, as well as classical test theory. The IRC, a non-modeling method of IRT, exposed not only the item parameters but also features of responses to each category using total scores. It will be helpful in the analysis of both dichotomous and polytomous data.