Statistics work only if I have a reference point

[trinityvixen]

So I did poorly on a chemistry test this week. I'm not fussed about it for a number of reasons--I've done well on other tests, this is a course I'm not sure I need, I've already taken it so I'm not concerned about knowledge I don't have. What I am is confused. I figured I'd throw this out to the people I know who know stats better than I ever have, do, or will.

Our grades are computed based on "z-scores," as befits a curve (apparently) that takes into account the fact we can drop one grade. This score equals [my score]-[test average]/standard deviation. The average z-scores of the class are then ranked. This is all well and good, but what rank/score equals what grade is not specifically ever stated. They say they chart the z-score averages, presumably on a histogram, and wherever there is a "break" in the graph--meaning a significant drop in the numbers of people at a given average z-score--there will be a change in letter grade. But since you have no idea where those breaks will be until all the tests are counted, including the final...what the hell will your grade be?

This is a useless way of keeping track of how well I'm doing. Also, pardon me and my non-statistical thinking here, but how does grading people based on how much better/worse they are than their peers accurately value what they've learned? This is not a new problem I know--this is the curse of the curve--but still!

Comments

[linaerys.livejournal.com]

I had a really good high school computer science teacher and most of the kids in the class had never done computer science before.

Your grading system sound really hard to understand.

[trinityvixen.livejournal.com]

I was the same way! I had a phenomenal physics teacher in high school--he was so good, I never had to study for standardized tests and I aced them. I was teaching my friends who had the I-have-tenure-and-will-retire-next-year guy. A lot of people in college physics were lost because they were coming into a hard subject with no background. Just a little bit of foreknowledge is a great thing.

I do not, even after reading all the explanations thus far offered, understand it still. I mean, I read the explanation they gave us. I see the scores go into the stats machine, but I cannot understand how they will come out. I get that they probably have a lot of people pissed off and demanding grade reviews (this is a course I'm betting is lousy with pre-meds). But there has to be a better way.