Appropriate class size for online courses?

What is the thinking these days about class size for online instruction? I was asked this question today. This is a question that online educators frequently examine. My professional recommendation, supported by the literature, is that online class sizes be limited to 15 to 20 students. Why? Here is what we know:

1. Attrition in online courses and programs is a problem. The attrition typically has three sources: inconsistent expectations, underdeveloped time management and self-directed learning skills, and lack of social presence. In terms of expectations, students continue to think that online courses are easier than on campus courses, that they will be able to fulfill the requirements of the course at their own pace, and so on. As for time management and self-directed learning skills, online educational opportunities tend to require students to take on more responsibility for tracking course requirements, due dates, and the like. Students need to be more autonomous than many of them are used to (e.g., the structure of on-campus courses and the weekly required face-to-face classes with professors tends to eliminate the need for students to manages a lot of the logistical overhead). In terms of social presence, if students experience limited to no connection with the professor and fellow students, they can feel disconnected, disengaged. If they have no voice, or feel that they have no voice, they don't/won't use it...and drift away.
   
   
2. Effective graduate-level teaching (whether online or on campus) involves students in relevant, meaningful projects that help prepare them for the profession; requires professors to provide high levels of constructive feedback; offers students multiple opportunities for exploration, practice, failure; engages students in mentoring and coaching relationships with faculty; involves highly engaging instructional experiences and formats; and so on.

Addressing the issues above (#1) in a way that reflects effective teaching practice (#2) is intensive, especially when the course is online. The transactional distance involved in an online course -- the fact that we are not all in the same room at the same time, and that we are working together asynchronously in a primarily text-based format -- exponentially increases the amount of time a professor needs to attend to the course and the students. So, when there are more than 20 students in an online course, something has to give, something suffers. Either the professor cannot adequately address the issues in #1, or has to significantly scale back the teaching approaches and strategies, or both.

Therefore, since we do not want to compromise on either front, my answer to the question is -- Allow online educators and students to get the most out of the educational opportunity by limiting class sizes to 15 to 20 students. Please.