The Relationship of Difficulty Index, Discrimination Index and Non-Functioning Distractor in One Best Answer Questions for Undergraduate Medical Program in Universiti Kebangsaan Malaysia

Creating high-quality one best answer (OBA) questions is crucial for valid medical student assessments, yet it presents a challenge. Issues like inappropriate difficulty index (D), poor discrimination index (R), and non-functional distractors (NFDs) can compromise assessment integrity. This study aimed to investigate the relationship between D, R, and NFD in OBA questions at Universiti Kebangsaan Malaysia (UKM) to improve item quality and assessment effectiveness. Using a quantitative approach, 499 OBA questions from the 2022/2023 academic session were analysed, including pre-clinical (Years 1 and 2) (393 questions) and clinical (Year 5) (106 questions), using the Smart Question Bank (SQB). We observed significant correlations and regressions in pre-clinical, items with more NFDs demonstrated a strong positive correlation with excessively easy items (D > 0.75) with (r = 0.81, p < 0.001) and yielded a statistically significant regression outcome (F = 279.86, p < 0.001). However, for the clinical had higher number of items with poor discrimination (R < 0.15) at 45.28% (n = 106), this indicated an inability of the item to differentiate between high and low-achieving students, and showed no significant correlation (r = 0.24, p = 0.059) and regression (F = 3.24, p = 0.059) with NFD. By identifying weaknesses via item analysis, this study provides insights for improving OBA question quality and guiding future item construction at UKM and other institutions.