Differentiating Among High-Achieving Learners: A Comparison of Classical Test Theory and Item Response Theory on Above-Level Testing

This study investigated the application of item response theory (IRT) to expand the range of ability estimates for gifted (hereinafter referred to as high-achieving) students' performance on an above-level test. Using a sample of fourth- to sixth-grade high-achieving students (N = 1,893), we conducted a study to compare estimates from two measurement theories, classical test theory (CTT) and IRT. CTT and IRT make different assumptions about the analysis that impact the reliability and validity of the scores obtained from the test. IRT can also differentiate students based on the student's grade or within a grade by using the unique string of correct and incorrect answers the student makes while taking the test. This differentiation may have implications for identifying or classifying students who are ready for advanced coursework. An exploration of the differentiation for Math, Reading, and Science tests and the impact the different measurement frameworks can have on classification of students are explored. Implications for academic talent identification with the talent search model and development of academic talent are discussed.