  In this study we coded, for individual student participation on each
question, the video of twenty-seven groups interacting in the group phase of a
variety of two-phase exams. We found that maximum group participation occurred
on questions where at least one person in the group had answered that question
incorrectly during the solo phase of the exam. We also observed that those
students that were correct on a question during the solo phase have higher
participation than those that were incorrect. Finally we observed that, from a
participation standpoint, the strongest (weakest) students seem to benefit the
most (least) from heterogeneous groups, while homogeneous groups do not seem to
favor students of any particular performance level.
