The grading in the Minnesota Model is preformed by the same TAs who teach discussion sections and labs. Having the same corps of TA allows for more useful feedback, both to the students and the teaching team. The Lecturers typically write the exams and the team decides on the emphasis of grading toward each problem or assignment.
In general, the following is how the overall course grade is computed:
All told less than 33% of the students grade is from working in groups, although since the students write individual lab reports, the actual percent of grade from group work is less than 20%.