The influence of representations on task difficulty in organic chemistry: an exploration using a novel paired-items test instrument

Abstract

The intricate relationship between representational competence and content knowledge in organic chemistry has been widely debated, and the ways in which representations contribute to task difficulty, particularly in assessment, remain unclear. This paper presents a multiple-choice test instrument for assessing individuals’ knowledge of fundamental concepts–such as nomenclature and basic reaction mechanisms–in organic chemistry using item pairs with and without representations. We conducted a pilot test of the instrument with 55 undergraduate students and administered the final version to 357 undergraduate chemistry students from seven German universities. We used the Rasch methodology for psychometric analysis to identify sound and reliable test properties. A task-difficulty comparison revealed no differences between the item pairs with and those without representations. Hierarchical regression suggests that the complexity and cognitive processes involved in a task influence its difficulty. Our data suggest that the relationship between representational competence and content knowledge may not be disentangled when item difficulty is considered. We argue that representational competence and content knowledge might not represent separate constructs, which is in line with the literature on representational dilemmas: representations cannot be taught without content knowledge, and content knowledge cannot be taught without the use of representations.