ICC-Based Projection of IRT/MIRT Response Functions Into DINA-Style Diagnostic Summaries

Assessments calibrated under item response theory are often expected to support diagnostic reporting, though their parameters differ from diagnostic classification models. This study introduces a projection procedure that summarizes continuous response functions into diagnostic metrics based on explicit reference distributions and mastery thresholds. These metrics—the projected nonmaster success summary, projected master success summary, and projected separation index—are conditional averages over defined mastery regions rather than portable parameters. Simulations and an empirical application show strong item-level agreement with recalibrated diagnostic models, while downstream classification showed varying sensitivity across calibration contrasts. Under a fixed reference distribution and threshold system, the projected separation index provided a conditional item-screening criterion and supported targeted warning-flag review.