Designing groups in problem-based learning to promote problem-solving skill and self-directedness

The effect of group size in problem-based learning (PBL) on the problem-solving skill, self-directedness, and technical knowledge of 72 students in a dental education program was examined. Pretest measures on self-directedness and technical knowledge were admin-istered to the 72 students. Equal numbers of students with low, medium, and high levels of self-directedness were randomly assigned to small, medium, and large PBL groups. Students then participated in a three-week PBL experience, which involved analyzing a patient case. After PBL was completed, posttest measures on self-directedness, technical knowledge, and problem-solving skill were assessed. Students' reactions to the PBL experience were also measured. Analysis of the data found that the development of self-directedness varied with group size. Students' self-directedness increased in small and medium size groups, but decreased in large groups. A significant difference was found between the medium and large groups on this measure. Furthermore, students in small groups rated 5 of 12 aspects of PBL significantly higher than did those in large groups, and students in medium size groups rated 10 of 12 aspects of PBL significantly higher than did those in large groups. Implications of these findings for instructional design theory, practice, and research are discussed.