A Monte Carlo comparison of item and person statistics based on item response theory versus classical test theory

Despite the well-known theoretical advantages of item response theory (IRT) over classical test theory (CTT), research examining their empirical properties has failed to reveal consistent, demonstrable differences. Using Monte Carlo techniques with simulated test data, this study examined the behavior of item and person statistics obtained from these two measurement frameworks. The findings suggest IRT- and CTT-based item difficulty and person ability estimates were highly comparable, invariant, and accurate in the test conditions simulated. However, whereas item discrimination estimates based on IRT were accurate across most of the experimental conditions, CTT-based item discrimination estimates proved accurate under some conditions only. Implications of the results of this study for psychometric item analysis and item selection are discussed.