The PI porposes to employ computer adaptive testing (CAT) to improve: STEM learning of Physics, test performance and student retention. The PI notes that this interdisciplinary, empirical proposal combines expertise in testing/measurement, cognition, and STEM education to diagnose students? problem solving and conceptual deficits prior to taking high-stakes course exams, and then to devise interventions aimed at remedying identified deficits in order to improve students? course performance and, ultimately, their retention in STEM disciplines. Working within the domain of physics at the undergraduate level, the research team will investigate the feasibility of using computer adaptive testing (CAT) techniques to devise a cognitively diagnostic computer adaptive testing (CD-CAT) tool that accurately predicts students? future performance on tests in difficult STEM introductory undergraduate courses prior to their administration. The potential findings will have relevance for other STEM disciplines, and if successful, for broadening participation.