An Experimental Design to Investigate Item Parameter Drift.

Methods for detecting item parameter drift may be inadequate when every exposed item is at risk for drift. To address this scenario, a strategy for detecting item parameter drift is proposed that uses only unexposed items deployed in a stratified random method within an experimental design. The proposed method is illustrated by investigating unexpected score increases on a high-stakes licensure exam. Results for this example were suggestive of item parameter drift but not significant at the .05 level.