Post-Validation of Multiple-Choice Questions in Microbiology

Background: Multiple Choice Questions (MCQs) are used to help understand the strengths and weaknesses of students and gaps in knowledge and provide feedback to teachers on their teaching methods.MCQs, therefore, should be valid and reliable.The statistical analysis of MCQs/items is done post-validation to check that they can adequately evaluate students' learning.Methods: A retrospective observational study of 72 solved MCQs was used for item analysis.Parameters that were analyzed included Difficulty Index (DIF), Discrimination index (DI) and Distracter effectiveness (DE).Results: Difficulty Index was 54.17% easy, 34.72% acceptable and 11.11% difficult.The Discriminatory Index (DI) calculation showed that 93.05% were poor, 3% acceptable, and 4.16% good.Among the MCQs with poor discrimination, there were 37.5% MCQs had negative discrimination, as low achievers answered these MCQs more than high achievers.The total number of distractors analyzed was 216 and the number of Non-Functional Distractors was 75 (NFD, those selected by < 5% of students), and functional distractors (FD) were 141(those chosen by >5% of students).Conclusion: An MCQ is ideal when it satisfies all three criteria, such as acceptable DIF 30-70 and acceptable DI 0.21-0.35,and has three functional distractors.In our study, only one MCQ satisfied acceptable DIF, DI and had three functional distractors.