How to assign individualized scores on a group project: an empirical evaluation

One major challenge in using group projects to assess student learning is accounting for the differences of contribution among group members so that the mark assigned to each individual actually reflects their performance. This research addresses the validity of grading group projects by evaluating different methods that derive individualized scores from group work. Both Monte Carlo simulation and real test data analyses were conducted. The four investigated methods are the within-group adjustment method, the partial adjustment method, the between-group adjustment method, and the expected contribution adjustment method. For all methods, a weighting factor is computed based on the peer and self ratings of contributions to the group project by group members. This study finds that individual differences have to be taken into account if group grades are going to be assigned and utilized for evaluating individual performance at all. Adjusting contribution differences based on peer and self ratings could be an effective way to improve the validity of group grades. Among the four studied methods, adjusting both the within-group and between-group contribution differences is the most effective, and is thus recommended for classroom use.