This study evaluated the psychometric properties of a self-report scale for assessing perceived driver competence, labeled the Self-Efficacy Scale for Driver Competence (SSDC), using item response theory analyses. Two samples of Swedish driving-license examinees (n = 795; n = 714) completed two versions of the SSDC that were parallel in content. Prior work, using classical test theory analyses, has provided support for the validity and reliability of scores from the SSDC. This study investigated the measurement precision, item hierarchy, and differential functioning for males and females of the items in the SSDC as well as how the rating scale functions. The results confirmed the previous findings; that the SSDC demonstrates sound psychometric properties. In addition, the findings showed that measurement precision could be increased by adding items that tap higher self-efficacy levels. Moreover, the rating scale can be improved by reducing the number of categories or by providing each category with a label.
Evaluating the reliability of multi-item scales: A non-parametric approach to the ordered categorical structure of data collected with the Swedish version of the Tampa Scale for Kinesiophobia and the Self-Efficacy Scale
