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Sunday, January 10, 2010

All large classes are not the same

Andrew Leigh points to a new study about class size at the university level that finds negative effects for classes over 100. This reminded me that one of my unfinished posts is a defense of large lectures - I may eventually post the whole thing but the core point is simply that all large classes are not created equal. Any study that tries to measure the impact of class size on some student outcome is going to be controlling for as many of the other things that affect that outcome as possible, like student and teacher characteristics (well, I should say, any well-designed study like the kind economists would want to see). But the reality is that when universities have discussions about increasing class sizes, ceteris is usually not paribus. So while I do believe that for any given instructor, students will likely be better off in smaller classes than larger, I also believe that a large lecture by one professor could easily be far better for students than a small lecture by another professor. Actually, as I write that sentence, it occurs to me that what I'm really saying is that I think any class size effect is going to be swamped by the individual teacher effect. I wonder if anyone has looked at that... At any rate, my point is that when people start railing about the evils of large lectures (which is not uncommon on my campus, and I readily admit that I used to be one of those people), I now tend to think that they really should be more careful about how they express themselves, that the problem is not necessarily large classes, in and of themselves, but large classes taught by people who have no idea how to teach large classes effectively.


  1. This is really a point about selection bias, isn't it? I mean, any department chair or associate dean or whoever's responsible for scheduling is likely to try to put people in large classes who will do best with them, right?

    Well, we can hope that's true.

    By the way, when you do write up the defense of large lecture classes, consider submitting it to the Journal of the Scholarship of Teaching and Learning.

  2. In theory, you're right and when we first started offering 500-seat sections, the idea was that only our best teachers would teach them. But over time, that has not really been maintained and with budget cuts, it could get worse - we are getting rid of all our part-time lecturers and next fall, we will probably offer only one 500-seat section each of micro and macro principles. Since the large courses count as two (we have a 3-3 load), we are going to start rotating who 'gets' to teach them and ability to teach them well is not part of the equation. Good times...

  3. You make a great point here. I see something similar with discussions of the value of teaching with clickers. The question shouldn't be "Does teaching with clickers improve learning?" It should be "What ways of teaching with clickers lead to better learning?" There are too many variables--and instructor choices--involved to look at a single variable (like the use of clickers or like class size) in isolation.


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