The extent of mismeasurement for aberrant examinees

The person-fit literature assumes that aberrant response patterns could be a sign of person mismeasurement, but this assumption has rarely, if ever, been empirically investigated before. We explore the validity of test responses and measures of 10-year-old examinees whose response patterns on a commercial standardized paper-and-pencil mathematics test were flagged as aberrant. Validity evidence was collected through postexamination reflective interviews with 31 of the 80 pupils flagged as aberrant and their teachers, and teacher assessment (TA) judgments for the whole examination cohort of 674 examinees. Analysis suggested that interview-adjusted scores were significantly better fitting than expected by chance, but only some adjustments suggest serious mismeasurement. In addition, disagreement between TA and test scores was significantly greater for aberrant examinees, and partially predicted the interview adjustments. We conclude that person misfit statistics when combined with TA might be a useful antidote to mismeasurement, and we discuss the implications for assessment research and practice. © Taylor & Francis Group, LLC.