Abstract:

The current study shows applications of both classical test theory (CTT) and item response theory (IRT) to psychology data. The study discusses item level analyses of General Mattering Scale produced by two theories as well as strengths and weaknesses of both measurement approaches. The survey consisted of a total of five Likert-type items. Each student chose the best answers from the given categories (e.g., not at all, a little, somewhat, very much). We specifically run generalized partial credit IRT model. Overall, we discussed that while CTT provides comparatively superficial information but, IRT allows gaining deeper insight into the test items and response categories. We concluded that the meaning of item properties differ in CTT and IRT, and this difference may lead to different interpretations. We aimed to encourage psychologists and counsellors to give more consideration to the IRT applications when assessing the psychometric features of the items. 

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