Item analysis of multiple choice questions: Assessing an assessment tool in medical students

Abstract

Aim: Assessment is a very important component of the medical course curriculum. Item analysis is the process of collecting, summarizing, and using information from student's responses to assess the quality of multiple-choice questions (MCQs). Difficulty index (P) and discrimination index (D) are the parameters used to evaluate the standard of MCQs. The aim of the study was to assess quality of MCQs. Materials and Methods: The study was conducted in the Department of Pathology. One hundred and twenty, 2nd year MBBS students took the MCQs test comprising 40 questions. There was no negative marking and evaluation was done out of 40 marks, and 50% score was the passing mark. Postvalidation of the paper was done by item analysis. Each item was analyzed for difficulty index, discrimination index, and distractor effectiveness. The relationship between them for each item was determined by Pearson correlation analysis using SPSS 20.0. Results: Difficulty index of 34 (85%) items was in the acceptable range (P = 30–70%), 2 (5%) item was too easy (P >70%), and 4 (10%) items were too difficult (P <30%). Discrimination index of 24 (60%) items was excellent (D >0.4), 4 (10%) items were good (D =0.3–0.39), 6 (15%) items were acceptable (D =0.2–0.29), and 6 (15%) items were poor (D < 0–0.19). A total 40 items had 120 distractors. Amongst these, 6 (5%) were nonfunctional distracters, 114 (95%) were functional distracters. The discrimination index exhibited positive correlation with difficulty index (r = 0.563, P = 0.010, significant at 0.01 level [two-tailed]). The maximum discrimination (D = 0.5–0.6) was observed in acceptable range (P = 30–70%). Conclusion: In this study, the majority of items fulfilled the criteria of acceptable difficulty and good discrimination. Moderately easy/difficult had the maximal discriminative ability. Very difficult item displayed poor discrimination, but the very easy item had high discrimination index, indicating a faulty item, or incorrect keys. The results of this study would initiate a change in the way MCQ test items are selected for any examination, and there should be proper assessment strategy as part of the curriculum development.