Tuesday, February 02, 2010

Does Class Size Matter?

Preliminary stats show 55 students in my algorithms course. That's probably close to the mean and slightly above the median. It's certainly not the largest course in the School of Engineering and Applied Sciences (SEAS), but it's up toward the top.

Why should I, or any faculty member for that matter, care about class size? For junior faculty, at least, there's a clear answer. A tenure case without some teaching of significantly sized classes is one with a weakness, opening the way to the arguments that the faculty member in question is working in an area of little interest (since nobody wants to take their classes in their area) or is providing insufficient service to the department (since they haven't taken on a large core course).

For senior faculty, I'm not so clear. While class sizes are listed in our annual review, I've heard no mention that they're considered of any particular importance -- or even of non-zero importance -- in determining annual raises. Indeed, I can't think of any direct benefit to me personally for teaching a large undergraduate class as opposed to a small one.* One might want to take on a big class to support one's department, as ostensibly money (and positions) should, in some way, follow students at the departmental level. I'd like to think that's how it works at many places; however, recent conversations with some higher-ups suggest that that connection is fairly tenuous for SEAS. Harvard's system in that respect seems to be broken. (If it wasn't, I think we'd be further ahead in our hiring in CS.)

So why should I care about my class size? Primarily, I suppose, personal pride. I take satisfaction in teaching students; the more qualified students, the better. (Not the more students the better, though; the more qualified students, the better...) Indeed, I've done the math, and while I'm quite sure Harvard does not calculate things this way, in my mathematical model I'm earning what Harvard's paying based solely on the number of students I teach. That helps me sleep at night.

Overall, however, this seems like an area where the incentive structure doesn't seem set up right. I can understand that class size isn't an end in itself; indeed, I can understand that part of the mission of the University is to preserve knowledge in areas that might be of narrow interest. (The Sanskrit, Slavic, Turkish, and Yiddish courses, for instance, have remarkably low numbers.) But it seems naive to think that size doesn't matter **, so it's slightly disturbing that when I think in terms of incentives, I'm ending up wondering why I should care about my class size at all.

* I do see a potential direct benefit for having my large graduate project class; some student projects can get turned into papers, and often students have me take part in turning their project into a paper, so I may get some research benefit from having a large graduate class. It's not clear that's a big benefit, but at least it's demonstrable.

** Yes, we all knew that was coming before the end of the post....


Gilbert said...

I had 4 classes in college taught with the Moore method, which pretty much demands an anemic class size. I wonder how those sorts of courses would factor in.

More generally, is it actually more useful or desirable to teach small, focused classes in favor of large classes? Certainly students stand to gain from the increased attention and time for class interaction. I imagine that small classes might also be a delight for teachers in ways that large classes never could.

Rasmus Pagh said...

In my university there is a clear incentive to teach larger classes: Each research group is supposed to do the same amount of teaching and supervision (measured in student-years). So if some group only teaches small classes, it has to do a lot of thesis supervision. It's a system that has advantages and disadvantages, but it is working pretty well for us.

Anonymous said...

I think personal pride is an excellent incentive, and the system works as whole. The department likely selects for people who care about teaching, and therefore would have the personal-pride incentive to teach well.

In fact, giving more direct incentives may even be counter-productive. If you did it because it was your job, or because your salary depended on it, you may lose the personal-pride motivation. If others could look at your large class sizes and say that "yeah, he teaches well because he wants to make more money", you would probably be slightly less proud of teaching well.

Further, the number of qualified students is basically impossible to measure. Direct incentives usually lead to neglect of the immeasurables. I as a teacher may be incentivized towards gimmicks that attract students, or even try to be known for giving out easy and good grades, which increases the measurable part (i.e. class size, rating) or my teaching quality. The immeasurable part (i.e. how qualified your students are) may suffer as a result. Any measurable effect (students taught by you getting good jobs) shows up in a very very noisy form in the very long run.

So imho, one must be careful when setting up incentives. Incentives encourage improvement in short-term easy-to-measure attributes, and can hurt long-term and harder-to-measure-but-often-very-important attributes. Of course not setting up any incentive structure may be bad as well, but in a setting where internal motivations work well, sometimes external motivations may result in an overall worse outcome. For an extreme example, imagine what would happen to wikipedia if people who edit pages were paid according to number of visits to the page. I think part of the financial meltdown can also be attributed to the way incentives were set-up in the financial industry.

Steven said...

"opening the way to the arguments that the faculty member in question is working in an area of little interest"

The class size is often not determined by level of interest. In a lot of CS programs, algorithms is a core course, so all of the majors and minors are required to take it. On the other hand, something like network security is typically optional. As a result, the size of the algorithms class is going to be much larger, regardless of which subject that students are more interested in.

Anonymous said...

@Anon 2:17pm: "The department likely selects for people who care about teaching"

My impression was actually that top departments are almost exactly the opposite. They select first for world-class researchers, and only a very distant second is teaching. Now, when we're talking about serious cream-of-the-crop researchers, I believe that many of them (particularly more senior ones) are very interested in teaching. But I doubt that's how they are selected for... Someone with more knowledge please correct me if I'm wrong.

- Different Anon

Swamped at State said...

I teach at a large state university, with large undergraduate classes. As with Harvard's SEAS, however, the connection between student-years and departmental budget is tenuous at best. Budgets are negotiated with the Dean/higher-ups every year. Class size is just one of many arguments we can use to justify a budget increase; as far as I understand, it is not a particularly weighty one.

We have pretty big disincentives to teach large classes:

- TA loads are only loosely correlated to class size. Last year I had one TA for 80+ students in a core required course, while some classes with <20 students also got a TA. Because of this, *large classes are significantly more work for me*.

- There are a number of senior faculty members who actively avoid taking on large classes of any kind. We have no transparent teaching load requirements, so basically you can teach very little if you are willing to throw your weight around (I actually have weight to throw, but dislike throwing it and enjoy teaching).

- Teaching doesn't count for much in promotion evaluations. As one former associate dean for research told me, "don't waste too much time on teaching".

So the only people who teach large classes are those who either like teaching (but then they are annoyed that it is not rewarded) or can't muscle their way out of it.

All this to say that yes, the incentive structure is wrong at my institution, perhaps even worse than at Ha'va'd; yes, size does matter (big classes have a high cost for me, even though they are quite, um, stimulating); changing the incentive structure requires getting senior faculty who don't teach much to pay some price for slacking off. This last point means that change is *very* hard to pursue.


Yours truly,
Swamped at State

BerkeleyProf said...

I also find teaching large classes much more work than small classes.

At Berkeley, we have a system where we receive a number of points for teaching a class, based loosely upon the size of the class. The larger the class, the more points you get (though not proportionate to class size). All faculty must teach a specified number of points per year (though really, it only needs to average out in the long term; it doesn't need to be exact in any particular year, it's OK if your balance wavers above or below the zero point).

This seems like an improvement over a system that makes no distinction between large and small classes.

Anonymous said...

I thought of taking your class but money is tight. I'm sticking to reading books for now. Keep up the good work, see you another time.