Impact of reduced idea density on pharmacy students' attainment in pharmaceutical calculations: a multicentre randomised controlled trial.

Idea density (ID) influences comprehension time when reading text. However, the effect of lowering ID on student performance in written exams remains unexplored. This two-arm, single-blind RCT aimed to investigate the effect of ID in pharmaceutical calculation exams.
Students were recruited from 11 UK schools of pharmacy and randomly assigned to two groups: A control and B intervention. Both groups received a baseline test and either a control or investigative test with lowered ID. Primary outcomes were group performance and pass rate in each test overall and on a question-by-question basis.
205 students completed the study. The pass rate increased when students completed questions with lower ID. No significant change in cohort group performance was seen when the overall score was compared (p=0.110). However, a statistically significant increase in performance was observed when group performance was analysed on a question-by-question basis (p=0.033, 95% CI [0.51, 9.76]). Furthermore, students in lower years had significantly improved pass rates when receiving lower ID questions (OR=3.76, p=0.028) with the attainment gap to higher year students also reduced to insignificant levels (p=0.421).
This suggests ID could be used as an objective measure to improve the comprehensibility of written exams when applied within sensible limits.