Answer to "What is an optimal PBL group size?"
In the original PBL design, the ideal group size was 5-8 students, allowing learners to contribute to the discussion and for the tutor or facilitator to keep track of individual students. It must be remembered, however, that when PBL was conceptualised, there were about 30 students in the PBL track, making it easy to manage. Most cohorts today exceed 200 students and so having groups with fewer than eight students is rare and probably unrealistic. Although several authors have recommended 8-10 students, Hung (2011) and Lim (2012) believe that in undergraduate programmes (where much support is required), a group size of more than eight undermines the perceived benefits of learning.
BARROW, H.S., and TAMBLYN, R.M. (1980). Problem-based Learning: An Approach to Learning. (New York: Springer).
HUNG, W. (2011). Theory to reality: a few issues in implementing problem-based learning. (Educ Tech Res Dev. 59:529-552).
LIM, W.K. (2012). Dysfunctional problem-based learning curricula: resolving the problem. (BMC Med Educ. 12:89.) https://bmcmededuc.biomedcentral.com/articles/10.1186/1472-6920-12-89