Over the last couple of years class sizes in the virtual classroom have grown in my job.   When we started we were at a maximum of 12 students per class, and we’re now at a point where we allow 30 students per class.   (This is with multiple instructors and assistants to help students).

There’s something I found which is worthy of note in virtual classrooms, and its the concept of critical mass.

When you talk to people about social networking, there is this concept of critical mass.   That is a minimum # of participants required in order for regular interaction to occur.   You see this a lot on public forums.   You’ll start with one person, and there are just a few postings, then you add a few more, and there are a few more postings, and a few more, etc, and you see linear growth.

Then at some point in your growth cycle you hit a “magic” threshold, and activity starts to grow exponentially.

What we discovered was the same rule was true for questions in virtual classes.   In a class size of 12 you might get 2-3 questions in a one hour lecture.   With a class size 20, you’d expect to see around 3-4.   However, when you hit 30, you don’t get the 6-9 questions, you’re more likely to get 15-20 questions.

Why is this important?

With lesson planning, and particularly live lectures, you plan for a give lecture + questions to take a specified period of time.   Lets take my job as an example.   Our “magic number” is that a lecture + demo should take 30 minutes, with 5 minutes at the end for questions.   So with my 12 students, that gave me roughly 36 seconds per question.

When we increase our class size to 30, we’d expect to see roughly 9 questions, at 36 seconds per question it only take 5.4 minutes to answer all those questions, so its still within our target range.

Instead, we don’t have 9 questions, we have 20.  This now takes 12 minutes total for the lesson.

No big deal right?

Wrong, now lets take our typical class, where we have that 35 minute lecture, followed by a 30 minute lab, and we do 4 lectures in a class. That’s a total of 260 minutes, or 4.3 hours.   That’s about as long as you can expect someone to retain information in a virtual setting spread across time.

When we got to 30 students, it’s now 288 minutes, coming in at 4.8 hours.  That’s a 27% increase in total time for delivery.   And that’s of course assuming that you only get those 30 questions.   We’ve seen instances where we have twice that after a  lecture due to this critical mass.

So if you’re a virtual instructor, the next time you get asked (and you will) to increase class size, remember there are pieces of the time equation that are linear, and other pieces, due to the concept of critical mass in social networks, that will increase geometrically.