Objective: This article introduces changes made to the diagnostic imaging (DIM) domain of the Part IV of the National Board of Chiropractic Examiners examination and evaluates the effects of these changes in terms of item functioning and examinee performance.
Methods: To evaluate item function, classical test theory and item response theory (IRT) methods were employed. Classical statistics were used for the assessment of item difficulty and the relation to the total test score. Item difficulties along with item discrimination were calculated using IRT. We also studied the decision accuracy of the redesigned DIM domain.
Results: The diagnostic item analysis revealed similarity in item function across test forms and across administrations. The IRT models found a reasonable fit to the data. The averages of the IRT parameters were similar across test forms and across administrations. The classification of test takers into ability (theta) categories was consistent across groups (both norming and all examinees), across all test forms, and across administrations.
Conclusion: This research signifies a first step in the evaluation of the transition to digital DIM high-stakes assessments. We hope that this study will spur further research into evaluations of the ability to interpret radiographic images. In addition, we hope that the results prove to be useful for chiropractic faculty, chiropractic students, and the users of Part IV scores.
Author keywords: Chiropractic, Educational Measurement, Diagnostic Imaging, Psychometrics
Author affiliations: IH, MAS, JKH, ARG, NET, MD, MS, MF: National Board of Chiropractic Examiners, Greeley, Colorado, United States
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