Psychometric analysis of questions associated with radiological images in the competitive examination for access to...

Psychometrics is a simple, intuitive approach used in educational research and in multiple-choice questionnaires. Since 2009, the competitive examination through which access to residency programs in Spain is determined (MIR) has included questions related to radiological images. The objective of this paper is to show the results of the psychometric analysis of these questions with the aim of comparing their degree of difficulty, discriminative capacity, and internal structure with respect to those of the other questions on the examination.

We analyzed all questions on the examination since 2009, classifying them as clinical cases with and without radiological images, clinical cases with and without non-radiological images, multiple choice questions, and negative questions. We used classical test theory and item response theory to assess the difficulty and degree of discrimination of the questions.

Of 225 questions, between 11% and 15% of the questions included in the examinations were associated with images. The questions associated with radiological images were more difficult (corrected difficulty index, 0.51) and had worse discriminative capacity. The increased difficulty of radiological questions was associated with worse discriminative capacity, especially if the clinical information provided was inadequate or if the clinical information was contrary to the radiological concept or if there had never been any questions about the concept in previoous MIR examinations.

To equalize the standards of the MIR examination, it is necessary to maintain an appropriate structure in devising radiology questions, with terms from the clinical context, appropriate use of distracters, and a lower level of difficulty, which could be achieved by using radiological images with typical radiological findings.