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Thursday, November 09, 2006

& Bad Teacher Tricks

Warning: Rant ahead.

So, I just got my grade on my first test in operating systems class, and it was a three-fold disappointment (for three different reasons). The score itself was a 69% - an abysmal score for somebody whose straight-A record wasn't broken until the third semester of college. However, next to the score was a letter grade - an A. That's right, an A. To add insult to double-injury, the teacher showed the grade distribution. Out of the whole class, there were two As. That means that my grade of 69 was either the best or the second best grade in the entire class.

It shouldn't take much effort at all to realize that something is very, very wrong with this situation. How could a 69% possibly be even the second highest score in the class? There appears to be a certain mentality to it - the teacher seems to believe that curving the scores makes up for abysmal test writing.

Another example of a test I had with this teacher was a problem involving B+ trees, using variable length name fields. I can't remember what the exact problem was, but after looking at it for a couple minutes I called the teacher over to ask about it. The conversation went something like this:
Me: Is it just me, or is it theoretically impossible to solve this problem?
Teacher: It's possible
Me: How? This buffer is too small to store this much data
Teacher: Just assume that the average length will be less than [some number I don't remember] [note that this could - in theory - work because if the average name length was small enough it would fit]
Me: That assumption isn't realistic at all, and is never suggested anywhere in the problem. In fact the problem kind of suggests that it wouldn't be true...

A similar incident (actually more than one) occurred on this test, only it was after the test had already been graded. He had built an implementation-specific algorithm assumption into the answer he counted as correct (without ever mentioning this assumption in the problem). If, like I did, you gave a more general answer that would be true regardless of implementation, you got a 0. His excuse for this was that the typical implementation allows this assumption, never mind the fact that we also discussed in class an alternate implementation which violates this assumption. This annoyed me all the more because I got a later problem wrong for making an "invalid" assumption about the problem, based on the fact that that's typically how it's done in practice.

Then there are the enjoyable classes where the teacher thinks that they can get away with bad tests without curving, simply by making homework weigh more in the class total, relying on the homework grade to bring up the overall scores to acceptable levels.

Let me state it very clearly: if your first or second highest score in the class is a 69%, there is something wrong with your tests. If you consider the ability to ask the teacher questions to be a good alternative to making your questions clear, there is something wrong with your tests. If you have to make non-test things have a very high weight to compensate for very low test scores, there is something wrong with your tests.

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