Another study by Leonard, Dufresne, and Mestre [8] found that students who were required to write qualitative strategies before solving problems were better at selecting which major principles apply to problems. In that study, a strategy was a written paragraph consisting of the major Principle, a Justification for why the principle is appropriate, and a general Procedure for applying the principle. In the following section, we explain how principle selection and strategy-writing have been adapted for the current CPS approach.