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Using differential item functioning to evaluate potential bias in a high stakes postgraduate knowledge based assessment.

ABSTRACT: Fairness is a critical component of defensible assessment. Candidates should perform according to ability without influence from background characteristics such as ethnicity or sex. However, performance differs by candidate background in many assessment environments. Many potential causes of such differences exist, and examinations must be routinely analysed to ensure they do not present inappropriate progression barriers for any candidate group. By analysing the individual questions of an examination through techniques such as Differential Item Functioning (DIF), we can test whether a subset of unfair questions explains group-level differences. Such items can then be revised or removed.We used DIF to investigate fairness for 13,694 candidates sitting a major international summative postgraduate examination in internal medicine. We compared (a) ethnically white UK graduates against ethnically non-white UK graduates and (b) male UK graduates against female UK graduates. DIF was used to test 2773 questions across 14 sittings.Across 2773 questions eight (0.29%) showed notable DIF after correcting for multiple comparisons: seven medium effects and one large effect. Blinded analysis of these questions by a panel of clinician assessors identified no plausible explanations for the differences. These questions were removed from the question bank and we present them here to share knowledge of questions with DIF. These questions did not significantly impact the overall performance of the cohort. Group-level differences in performance between the groups we studied in this examination cannot be explained by a subset of unfair questions.DIF helps explore fairness in assessment at the question level. This is especially important in high-stakes assessment where a small number of unfair questions may adversely impact the passing rates of some groups. However, very few questions exhibited notable DIF so differences in passing rates for the groups we studied cannot be explained by unfairness at the question level.

SUBMITTER: Hope D

PROVIDER: S-EPMC5883583 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Using differential item functioning to evaluate potential bias in a high stakes postgraduate knowledge based assessment.

Hope David D Adamson Karen K McManus I C IC Chis Liliana L Elder Andrew A

BMC medical education 20180403 1

<h4>Background</h4>Fairness is a critical component of defensible assessment. Candidates should perform according to ability without influence from background characteristics such as ethnicity or sex. However, performance differs by candidate background in many assessment environments. Many potential causes of such differences exist, and examinations must be routinely analysed to ensure they do not present inappropriate progression barriers for any candidate group. By analysing the individual qu ...[more]

PMID: 29615016

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Project description:ObjectiveTo assess differential item functioning (DIF) in an item pool measuring the mobility of hospitalized patients across educational, age, and sex groups.DesignMeasurement evaluation cohort study. Content experts generated DIF hypotheses to guide the interpretation. The graded response item response theory (IRT) model was used. Primary DIF tests were Wald statistics; sensitivity analyses were conducted using the IRT ordinal logistic regression procedure. Magnitude and impact were evaluated by examining group differences in expected item and scale score functions.SettingHospital-based rehabilitation.ParticipantsHospitalized patients (N=2216).InterventionsNot applicable.Main outcome measuresA total of 111 self-reported mobility items.ResultsTwo linking items among those used to set the metric across forms evidenced DIF for sex and age: "difficulty climbing stairs step-over-step without a handrail (alternating feet)" and "difficulty climbing 3-5 steps without a handrail." Conditional on the mobility state, the items were more difficult for women and older people (aged ≥65y). An additional 18 items were identified with DIF. Items with both high DIF magnitude and hypotheses related to age were difficulty "crossing road at a 4-lane traffic light with curbs," "jumping/landing on one leg," "strenuous activities," and "descending 3-5 steps with no handrail." Although DIF of higher magnitude was observed for several items, the scale-level effect was relatively small and the exposure rate for the most problematic items was low (0.35, 0.27, and 0.20).ConclusionsThis was the first study to evaluate measurement equivalence of the hospital-based rehabilitation mobility item bank. Although 20 items evidenced high magnitude DIF, 5 of which were related to stairs, the scale-level effect was minimal; however, it is recommended that such items be avoided in the development of short-form measures. No items with salient DIF were removed from calibrations, supporting the use of the item bank across groups differing in education, age, and sex. The bank may thus be useful to assist clinical assessment and decision-making regarding risk for specific mobility restrictions at discharge as well as identifying mobility-related functions targeted for postdischarge interventions. Additionally, with the goal of avoiding long and burdensome assessments for patients and clinical staff, these results could be informative for those using the item bank to construct short forms.

Dataset Information

Using differential item functioning to evaluate potential bias in a high stakes postgraduate knowledge based assessment.

Publications

Using differential item functioning to evaluate potential bias in a high stakes postgraduate knowledge based assessment.

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