• Vol. 35 No. 2, 67–71
  • 15 February 2006

Relationship Between Item Difficulty and Discrimination Indices in True/False-Type Multiple Choice Questions of a Para-clinical Multidisciplinary Paper



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Introduction: This paper reports the relationship between the difficulty level and the discrimination power of true/false-type multiple-choice questions (MCQs) in a multidisciplinary paper for the para-clinical year of an undergraduate medical programme.

Materials and Methods: MCQ items in papers taken from Year II Parts A, B and C examinations for Sessions 2001/02, and Part B examinations for 2002/03 and 2003/04, were analysed to obtain their difficulty indices and discrimination indices. Each paper consisted of 250 true/false items (50 questions of 5 items each) on topics drawn from different disciplines. The questions were first constructed and vetted by the individual departments before being submitted to a central committee, where the final selection of the MCQs was made, based purely on the academic judgement of the committee.

Results: There was a wide distribution of item difficulty indices in all the MCQ papers analysed. Furthermore, the relationship between the difficulty index (P) and discrimination index (D) of the MCQ items in a paper was not linear, but more dome-shaped. Maximal discrimination (D = 51% to 71%) occurred with moderately easy/difficult items (P = 40% to 74%). On average, about 38% of the MCQ items in each paper were “very easy” (P≥75%), while about 9% were “very difficult” (P <25%). About two-thirds of these very easy/difficult items had “very poor” or even negative discrimination (D ≤20%).

Conclusions: MCQ items that demonstrate good discriminating potential tend to be moderately difficult items, and the moderately-to-very difficult items are more likely to show negative discrimination. There is a need to evaluate the effectiveness of our MCQ items.

Multiple-choice questions (MCQs) are used more and more in departmental examinations or as comprehensive examinations at the end of an academic session. They may be used to determine progress or to make decisions regarding the certification of a candidate.

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