의학전문대학원의 임상과목 지필시험에서 변별도 지수들과 라쉬모형에 의한 문항반응이론의 비교

A Comparison between Discrimination Indices and Item‐Response Theory Using the Rasch Model in a Clinical Course Written Examination of a Medical School

Purpose: The reliability of test is determined by each items characteristics. Item analysis is achieved by classical test theory and item response theory. The purpose of the study was to compare the discrimination indices with item response theory using the Rasch model. Methods: Thirty‐one 4th‐year medical school students participated in the clinical course written examination, which included 22 A‐type items and 3 R‐type items. Point biserial correlation coefficient (Cpbs) was compared to method of extreme group (D), biserial correlation coefficient (Cbs), item‐total correlation coefficient (Cit), and corrected item‐total correlation coeffcient (Ccit). Rasch model was applied to estimate item difficulty and examinee s ability and to calculate item fit statistics using joint maximum likelihood. Results: Explanatory power (r2) of Cpbs is decreased in the following order: Ccit (1.00), Cit (0.99), Cbs (0.94), and D (0.45). The ranges of difficulty logit and standard error and ability logit and standard error were -0.82 to 0.80 and 0.37 to 0.76, -3.69 to 3.19 and 0.45 to 1.03, respectively. Item 9 and 23 have outfit ≥1.3. Student 1, 5, 7, 18, 26, 30, and 32 have fit ≥1.3. Conclusion: Cpbs, Ccit, and Cit are good discrimination parameters. Rasch model can estimate item difficulty parameter and examinee s ability parameter with standard error. The fit statistics can identify bad items and unpredictable examinee s responses.