The students in the elementary teachers class made up data and did not actually perform the experiment. I want students to take responsibility for climate-building. I have sometimes given them surprise quizzes asking, for instance, to name the other people in their group. I often discuss with them after the fact the need to create a cooperative climate. Students say one unique thing about them.
Students introduce others to the class.
I have used a survey form to get the best match possible and most often the match is based on time available. When a person did not wish to become involved in this type of activity, that person or persons became a member of my study group. The background survey seems to work well. I did this for some semesters. Each team usually consists of a student good in math, one good in computer.