The use of ratio and proportion, dimensional analysis, and equations to solve pharmacy calculations problems

To evaluate the effects of using different problem-solving approaches on the success rates of student pharmacists in solving problems throughout a pharmacy calculations course.

A survey was administered to first-year students (N = 96, response rate 100%) near the completion of a pharmacy calculations course. The survey assessed whether students used the approaches of ratio and proportion (RP) or equations vs. dimensional analysis (DA) to solve calculation problems involving conversions, weight-based doses, flow rates, electrolyte solutions, and expressions of concentration. Questions used on course exams were tagged according to topics. Mean success rates in solving tagged questions were correlated with the problem-solving approaches that students used.

Approximately 60% of students used RP/equations, 30% used DA, and 10% used both approaches equally. The success rate of students solving conversions was 74% ± 24% for RP, 84% ± 14% for DA (P < .05 vs. RP), and 91% ± 12% for the use of both approaches equally (P < .05 vs. RP). Success rates in solving calculation problems of weight-based doses, flow rates, electrolyte solutions, and expressions of concentration were similar across all approaches.

The use of DA, or the combination of RP and DA equally, may be advantageous for solving conversions but not for the other types of calculation problems studied. Therefore, for most topics, pharmacy calculations instructors can demonstrate the method of their choice. Since a considerable number of students use each of the approaches, the demonstration of both approaches in class may be advantageous.