Swiss general internal medicine board examination: quantitative effects of publicly available and unavailable questions on question difficulty and test performance.

Background: Formerly, a substantial number of the 120 multiple-choice questions of the Swiss Society of General Internal Medicine (SSGIM) board examination were derived from publicly available MKSAP questions (Medical Knowledge Self-Assessment Program®). The possibility to memorise publicly available questions may unduly influence the candidates' examination performance. Therefore, the examination board raised concerns that the examination did not meet the objective of evaluating the application of knowledge. The society decided to develop new, "Helvetic" questions to improve the examination. The aim of the present study was to quantitatively assess the degree of difficulty of the Helvetic questions (HQ) compared with publicly available and unavailable MKSAP questions and to investigate whether the degree of difficulty of MKSAP questions changed over time as their status changed from publicly available to unavailable.

Methods: The November 2019 examination consisted of 40 Helvetic questions, 40 publicly available questions from MKSAP edition 17 (MKSAP-17) and 40 questions from MKSAP-15/16, which were no longer publicly available at the time of the examination. An one factorial univariate analysis of variance (ANOVA) examined question difficulty (lower values mean higher difficulty) between these three question sets. A repeated ANOVA compared the difficulty of MKSAP-15/16 questions in the November 2019 examination with the difficulty of the exact same questions from former examinations, when these questions belonged to the publicly available MKSAP edition. The publicly available MKSAP-17 and the publicly unavailable Helvetic questions served as control.

Results: The analysis of the November 2019 exam showed a significant difference in average item difficulty between Helvetic and MKSAP-17 questions (71% vs 86%, p <0.001) and between MKSAP-15/16 and MKSAP-17 questions (70% vs 86%, p <0.001). There was no significant difference in item difficulty between Helvetic and MKSAP-15/16 questions (71% vs 70%, p = 0.993). The repeated measures ANOVA on question use and the three question categories showed a significant interaction (p <0.001, partial eta-squared = 0.422). The change in the availability of MKSAP-15/16 questions had a strong effect on difficulty. Questions became on average 21.9% more difficult when they were no longer publicly available. In contrast, the difficulty of the MKSAP-17 and Helvetic questions did not change significantly across administrations.

Discussion: This study provides the quantitative evidence that the public availability of questions has a decisive influence on question difficulty and thus on SSGIM board examination performance. Reducing the number of publicly available questions in the examination by introducing confidential, high-quality Helvetic questions contributes to the validity of the board examination by addressing higher order cognitive skills and making rote-learning strategies less effective.