Yesterday, just before Harvard's spring break, I gave the midterm for my undergraduate class, and then we spent the afternoon grading it. Hopefully, students don't actually read my blog, so they won't be anxious and disappointed over break. Because on average, they didn't do well.
My midterms are commonly both difficult and long; most students don't finish, and historically the average has been around 65-70%. This year, the average was about 50%.
I'm looking for possible explanations. Here's what I've come up with so far.
1) The test was harder this year. There may be something to that -- some of the new questions I've never used before people did quite poorly on. On the other hand, I also think the class did statistically significantly worse on some of my old stand-by questions than in previous years. This may account for some of the discrepancy -- possibly the top students, who usually can do almost everything on the exam, might have obtained lower scores than usual because of this -- but I don't think it can explain this big a discrepancy.
2) I'm teaching worse this year. There may be something to that -- I am teaching two classes this semester and I do have a 9-month old to cope with -- but I doubt this is an explanation. (Obviously, I'm a bit biased here.) My class doesn't vary significantly from year to year -- same topics, same lecture notes this year as usual. Again, even if I think this had an effect, I don't think it can explain this big a discrepancy. (Similarly, I don't think the issue is the TAs I have this year -- they seem like a really great bunch.)
3) The students are doing less well this year. Unfortunately, here there's some evidence -- the average scores, on the whole, are noticeably lower this year than last year across all assignments so far. That could be variance in TA grading style, and the discrepancy on assignments is nowhere as large as it was with the midterm. But my thought is that perhaps this is an unfortunate flip side to class sizes increasing. The class enrollment has dropped from the mid-80s down to 80 -- but this is still over twice as many people as were taking it last year, and still my second largest class ever. Does larger class size (less self-selection) translate into lower averages?
4) Random chance. Seems unlikely.
5) External considerations outside my scope. Maybe more students are having to deal with other midterms the same day or week this year than usual. Small changes in the class schedule can have big effects this way, since many people have multiple classes in common.
Whatever the reason, it's a situation I'll have to pay some attention to. I may have to adjust the pace and style of the lectures, to better maximize what students learn. But for now, I've got the midterm blues. Yes, professors get them too.