Background: In problem-based learning (PBL), high-quality discussions are crucial for student learning. The quality of the discussion is affected by the quality of the contributions students make during PBL tutorials.
Aim: This study investigated whether students are able to evaluate the activities of their peers in PBL groups in a reliable and valid way.
Method: For this purpose, the Maastricht-Peer Activity Rating Scale (M-PARS) was developed. The M-PARS was well-founded on the literature about effective tutorial performance. With this scale, students (N = 196) were evaluated by their peers on three main aspects: their constructive, collaborative, and motivational contributions to the group.
Results: A confirmatory factor analysis demonstrated that the data fitted the three-factor model reasonably well. The generalizability studies demonstrated good internal consistency when students were evaluated by, at least, four of their peers. Furthermore, Hancock's coefficients indicated good construct reliability.
Conclusions: The results prove that peers are able to provide reliable and valid information about a student's active participation in the tutorial group, if at least four peer ratings are attainable, out of a group of eight students. In conclusion, the M-PARS is a valid and reliable instrument.