Item Parameter Drift in Context Questionnaires from International Large-Scale Assessments

The purpose of the current study was to examine the impact of item parameter drift (IPD) occurring in context questionnaires from an international large-scale assessment and determine the most appropriate way to address IPD. Focusing on the context of psychometric and educational research where scores from context questionnaires composed of polytomous items were employed for the classification of examinees, the current research investigated the impacts of IPD on the estimation of questionnaire scores and classification accuracy with five manipulated factors: the length of a questionnaire, the proportion of items exhibiting IPD, the direction and magnitude of IPD, and three decisions about IPD. The results indicated that the impact of IPD occurring in a short context questionnaire on the accuracy of score estimation and classification of examinees was substantial. The accuracy in classification considerably decreased especially at the lowest and highest categories of a trait. Unlike the recommendation from literature in educational testing, the current study demonstrated that keeping items exhibiting IPD and removing them only for transformation were appropriate when IPD occurred in relatively short context questionnaires. Using 2011 TIMSS data from Iran, an applied example demonstrated the application of provided guidance in making appropriate decisions about IPD.