A Comparison of Item Type and Source on Difficulty and Discrimination Ability

Difficulty and discrimination ability were compared between multiple choice and short answer items in midterm and final examinations for the internal medicine course at Louisiana State University School of Dentistry. The examinations were administered to 67 sophomore dental students in that course. Additionally, the impact of the source of the information, either lecture or text, on the accuracy of the response was studied. Data were collected from a total of 177 students during the three years of the study. Item analysis provided a difficulty index, and a discrimination index from the top 27 percent minus the lower 27 percent divided by 100. Kuder Richardson 20 was computed for each test, with values ranging from 0.59 to 0.68. Although it had been expected that short answer items would be the more difficult and best discriminators, the percentages of difficult or discriminating items did not vary greatly for item type or source, and neither factor produced a consistent trend. (SLD)