Find the ideal study group size for efficiency.
Study groups have an upper bound set by airtime. Session length divided by group size gives each person's share, but the divisor is not the only problem — each additional member also costs a few percent of the session to coordination, so usable minutes fall as the group grows. Comparing the resulting airtime against what each person needs to contribute is what identifies the size at which a group stops working.
Usable session time
Efficiency = 1 - coordination loss x (group size - 2); usable minutes = session length x efficiency
Airtime
Airtime per person = usable minutes / group size
Three to five for discussion-based work. Below three there is too little diversity of understanding; above six, airtime and accountability both fall away quickly.
Because individual airtime collapses and social loafing rises. With eight people in a ninety-minute session, each person speaks for around nine minutes at best.