Group size and interactions in online courses

The Open University (OU) in England was set up in 1969 by the UK government to widen access to higher education. The university has over 160,000 students, almost all studying ‘off-campus’, currently categorised as distance learning in the HESA data, but this term may need updating. The OU has had a long-standing principle of splitting cohorts into groups of 25 students. With almost all UK courses currently delivered entirely online due to a lockdown, I want to know what effect group size has on interaction levels? Is there an optimum group size for highly interactive online courses?

Cohort numbers are important as we want to run courses with lots of interaction where students engage in active and collaborative learning that improves their outcomes. It is vital to keep costs down by controlling the volume of staff interaction provided, so classes are sustainable and represent value for money. We also want a balance for students with opportunities for interactions, but they do not feel lost and disconnected.

My first search found a great quote from a 1969 paper from The Journal of Social Psychology; ‘ group size increases, individual participation decreases.‘ While this paper looked at on-campus, free discussion within small groups, it was a good starting point. With groups of two students, they have to be highly engaged, whereas groups of five provide individuals with a space to hide or take a step back. 

However, anecdotally from my teaching days, sometimes larger groups can create exciting conversations and develop a social norm of participation that does not happen in smaller groups. I assume that optimum group size might differ for synchronous and asynchronous learning activities, between different pedagogic approaches, teacher expectations and interaction levels, and technical and non-technical subjects.

Group sizes

I found some recommended size ranges include Sieber (2005)‘s 12 for instructors new to teaching online and Tomei (2006)‘s suggestion of 12 for postgraduate courses. Colwell and Jenks (as cited in Burruss, Billing, Brownrigg, Skiba, & Connors, 2009) suggest an upper limit as 20 for undergraduate and 8 to 15 for postgraduate. In a paper by Parks-Stamm et al. (2017), student interaction in classes of 14 or fewer students increased with more instructor participation, but this mattered less with larger groups of 15-30 students. Orellana (2006) states that 16 was perceived as the optimal group size by academics teaching online to achieve the highest level of interaction.

An Inside Higher Ed article interviewed several American universities with established online portfolios asking about optimum group size. The University of Massachusetts at Lowell have 28,000 online enrollments; they cap their undergraduate classes at 27 and postgraduate courses at 25 students. Granite State College in New Hampshire keep group sizes between 12-15 students, and on the other end, Brigham Young University at Idaho’s average class size is 37. The WCET a digital learning policy group for universities sets a ‘rule of thumb’ of 20-25 students.

Initial recommendations

I could not find anyone in my short search that recommended group sizes of over 27 students, but there were many suggestions that group size is not the best metric to use. Starting with the OU’s suggested groups of 25 students and then monitoring each is a good starting point. You can then monitor student performance, withdrawals, instructor response time, engagement measures, including the volume of student/instructor interactions, and student feedback. This data will allow you to assess if the group size, interaction levels, and course design meet the students’ learning and social needs. You could also provide regular opportunities for small-sized groups, including 2-3 students working together for students who would benefit from more intense interactions.