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.