Does anyone have data on determining the appropriate size of a class that has lab exercises included? The class is for adult learners on a business function.

There is no data because there are so many factors involved. Do people need to move around freely? Do you need tables? Just chairs? What types of activities are there? How much interaction will there be? How experienced is the facilitator? How much time do you have? Etc. etc. etc....

I've seen amazing, interactive classes taught to a room of 100 people and lousy classes taught in a room of only 8... there are no hard fast rules. I believe anyone who claims otherwise is trying to sell you something.