Thirty materials engineering students solved four problems which varied in level of complexity as well as closed- and open-endedness. Students scored lower on more complex problems, but scored higher on open-ended problems. However, students who solved the problems in a think aloud setting expressed greater discomfort with the open-ended problems because of the lack of constraints provided by these problems. Students dealt with the ambiguity of the open-ended problems in a variety of ways. Some students provided ambiguous answers while others added their own constraints to the problems. The manner in which problems were scored may have contributed to the unexpected finding that students scored higher on open-ended problems.