Difficulty Index, Discrimination Index and Distractor Efficiency in Multiple Choice Questions
Objective: Our first objective was to evaluate the quality of MCQs by analyzing difficulty index, discrimination index and distractor efficiency. Our second objective was to find out the association of MCQs having good difficulty and discrimination indices with distractor efficiency.
Methodology: This cross-sectional study was conducted at department of Pathology, Islamabad medical and dental college. Midterm paper comprising of total 65 MCQs was assessed for difficulty index (DIF), discrimination index (DI) and distractor efficiency (DE). Data was entered in Microsoft Excel 2010 and SPSS 21. Quantitative variables were expressed as mean±SD. Qualitative variables were written as number and percentage. Independent t-test was applied to find out the association of DIF and DI with DE.
Results: According to DIF, out of total 65, 53(81%) MCQs were in acceptable category, only 1(2%) MCQ was too difficult and 11(17%) were too easy. Regarding DI, total 34(62%) MCQs showed excellent discrimination tendency to distinguish low and high performer students. While 15(23%), 5(8%) and 11(17%) MCQs demonstrated good, acceptable and poor discrimination ability respectively. Out of total 260 distractors, 72% were functional and only 28% were non-functional. Total 16(25%) MCQs had zero non-functional distractor (NFDs), while 30(46%) and 16(25%) MCQs had 1 and 2 NFDs respectively. Only 3(5%) MCQs were with 3 or more NFDs. DE was significantly more (100%) in 1 difficult item as compared to 11 easy items in which DE was less (36.33%). However, DE in MCQs having poor and good DI was almost same.
Conclusion: In this paper of Pathology, large number of MCQs have acceptable level of DIF (81%) and DI (83%). Distractor efficiency related to presence of zero or 1 NFD is 71%. Through item analysis, standardized MCQs having average DIF, high discrimination power with large number of functioning distractors can be developed. Thus it is an effective way to improve the validity of examination and to efficiently assess the student performance.