Peers play an important role in an individual's learning via collaboration. This study examined three semesters worth of student data collected through collaborative exams in a calculus-based introductory physics course. Participants were asked 142 physics problems over two rounds, and they answered the problems first individually (first round) and then with their groups (second round). Based on the group type determined by the number of correct answers, a majority of correct or incorrect answers, and a variety of answers in the individual round, we examined how group type affects group performance in the group round. A majority of correct and incorrect answers and the variety of answers in the individual round were important for group-round performance. The percentage of finding the correct answer in the group round was directly proportional to the number of students with correct responses in the individual round. Furthermore, an increase in the number of correct answers in the individual round increased the group performance when similar conditions were seen in the majority of correct and incorrect answers and the variety of answers in the previous round.