Thursday, February 18, 2010

PH253: Exam 1 results

The exam scores are in. You'll get them back in class on Thursday; see the previous post for how to check the scores online.

There is of course good news and bad news. The good news is that I think most of you are getting the concepts, but there are a few specific points we need to go over. The bad news is somewhat more multi-faceted.

The less good news is that your mechanics is, by and large, rusty. It has been a while since PH105 for most of you, and I could tell. Understandable, but it hurt.

The bad news is, I suppose, that the math really hurt a lot of you. As with mechanics, Calculus has been a long time back for some of you, and I could tell. Another thing that really hurt was not catching tiny, but important, differences between homework or example problems and the exam problems.

Anyway: the raw exam average, with generous partial credit, was about 66%, with a bimodal distribution (see below). That I considered to be an unacceptable result. What I did, rather than just scaling the whole thing, was to make your score your best 3 out of the 4 problems. This seemed to be the most fair thing without unfairly penalizing either the high or low end of the distribution, and is consistent with the fact that time was clearly a factor on this thing. Below are some interesting (to me anyway) plots. Two of them show the percentage choosing each question and the average score of those, a third shows the original distribution, and the last shows the "best 3 of 4" grade distribution, which is what I'm adopting. (click for a larger image)

I guess ultimately, then, I am not really terrified or saddened by the results, but I think it is worth the time to spend most of Thursday's class going over the test and reviewing the material before we move on to new things. My impression is that most of you have the concepts down, but either miss one or two small things, or are getting stuck on the execution (meaning, largely, the math).

I want to stress: there is no reason for panic at this stage. If you are worried about your grade, the homework will save you if you just keep at it. A good homework score can make up for one low exam score. There is plenty of time left to raise a grade, and it is likely that I'll give some sort of extra credit option soon. With almost no exceptions, you can all still pass the class, no question.

Really. Don't panic.

Some random notes: question 3 was not popular, which worried me a bit -- that was one hint to me that many of you are not comfortable with calculus anymore. Number 6 was not popular either, but it was a bit subtle. Question 4 seemed reasonable enough, but it had a lot of places to go wrong. Plus, many of you didn't catch the difference between it and the example problem.

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