I am having students complete a presentation as a group project. Each student's grade will have two components: an instructor grade, from me, and a group grade from their group.
The group grade is calculated as the sum of five elements, each graded out of five, for a maximum of 25 points from each member of the group. Each student's 'group grade' is then calculated as the average of scores from the group.
The problem I have is that some of the groups have 4 students, some 5, and some 6. This means that weight of the score for students in larger groups is less than for those in smaller groups.
I plan to compensate for this by weighting the instructor grade more heavily. But as I think about it, even this doesn't cancel out the discrepancy.
How can I weight, or adjust, my grading scheme to make sure it's as fair as possible?