Assessing person-fit on measures of typical performance

We present statistical and theoretical issues that arise from assessing person-fit on measures of typical performance. After presenting the status of past and current research issues, we describe three topics of ongoing concern. First, because typical performance measures tend to be short, and because they have low bandwidth, the detection of person-misfit is often attenuated. Second, there is a need for creative methods of identifying the specific sources of response aberrancy, rather than simply identifying person-misfit. Third, the promise of person-fit measures as moderators of trait-criterion relations remains undemonstrated. We offer commentary or potential resolutions to these three current topics. In terms of future research directions, we outline two lines of advancement that are relevant for both educational and personality psychologists. These are (a) the use of person-fit statistics in the assessment of how item response theory measurement models differ across manifest groups (e.g., ethnicity, gender), and (b) the application of person-fit statistics under ''external'' item response theory model conditions. We summarize the role these advances could play in helping educational testers go beyond the standard task of identifying ''invalid'' protocols by discussing how person-fit assessment may contribute to our understanding of individual and group differences in trait structure.