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Abstract:
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This paper describes the exploration of dimensionality of the CAOS test that was designed to measure students' conceptual understanding of important statistical ideas, across three years of revision and testing, content validation, and reliability analysis based on classical test theory (CTT). Even though there is controversial in determining dimensional structures, such as unidimensional, multidimensional and bifactor models, based on item response theory (IRT), test developers often apply unidimensional IRT regardless of further consideration. Moreover, linear and nonlinear factor models are often used without careful consideration. I will explore the dimensional structure of the CAOS test with the full information item factor analysis implemented in TESTFACT program and present the results in the differential item/test functioning (DITF) obtained by LINKDIF program.
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