Comparison of Item Statistics of Physics Achievement Test using Classical Test and Item Response Theory Frameworks

Abstract

In this study, the author examined the comparability of item statistics generated from the frameworks of classical test theory (CTT) and 2-parameter model of item response theory (IRT). A 60-item Physics Achievement Test was developed and administered to 724 senior secondary school two students (Age 16-18 years), who were randomly selected from 16 senior secondary schools in Ibadan Educational Zone I, Oyo State, Nigeria. Results showed that item statistics obtained from both frameworks were quite comparable. However, item statistics obtained from IRT 2-parameter model appeared more stable than those from CTT. Moreover for item selection process, IRT 2-parameter model led to deletion of fewer items than CTT model. This result implies that test developers and public examining bodies should integrate IRT model into their test development processes. Through IRT model, test constructors would be able to generate more reliable items than in the CTT model being currently used and ultimately the test scores of examinees will be more reliably estimated.

Keywords: Item statistics; Item analysis; Item response theory; Classical test theory; Physics Achievement Test.