When grade point averages (GPAs) are used for admission into tertiary education, there is an implicit assumption that any two identical GPAs convey the same level of academic competency. However, this assumption does not hold when students are free to choose elective subjects and there are differences in their difficulty and dimensionality.
In this study, we utilized item response theory to examine dimensionality and difficulty of 11 elective subjects in Norwegian high school, while accounting for self-selection bias, using data from 21,666 third year students.
Our results show that the GPA is best represented as a multidimensional construct. Additionally, we demonstrate that the selection bias in observed subject grade averages for electives conceals considerable differences in difficulty levels. Hence, the GPA of Norwegian high school students does not only reflect academic competency but also the decisions made regarding which elective subjects to take.
Ofstad, Sverre Berg; Tan, Tony & Andersson, Björn (2026). Comparing the difficulty of elective subjects in high school using a population-based Norwegian registry. Scandinavian Journal of Educational Research. ISSN 0031-3831. doi: 10.1080/00313831.2026.2648976.