The act of evaluating solutions is a common engineering design activity. Over the past eight years we have used verbal protocol analysis to gain insight into engineering students' design processes. This study includes protocols from 32 freshmen and 61 seniors who solved 2 design problems that differed in complexity. In this dataset, 18 of the subjects solved the same problems as both freshmen and seniors. This dataset has allowed us to characterize differences between freshmen and seniors on a global scale as well as an individual scale. Additionally, the inclusion of two problems that vary in complexity allows us to analyze differences in performance and behaviors across problems. One of the important findings that has emerged from an across problem comparison is differences in the amount of time that students spent evaluating their solutions. In particular, (i) students spent more time evaluating their solutions and (ii) a greater number of students evaluated their solutions when solving a more "complex" problem as compared to a less "complex" one. In this paper, we present these results and discuss reasons for these differences. These include differences in the complexity of the two problems and the kinds of processes students employed while designing their solutions. We will also discuss the relationships between time spent evaluating and the number of constraints considered (constraints either given or introduced by the student). We conclude this paper with a summary of implications for engineering education.
