Trying to make sense of an SAT score

[ultrafilter]

My sister took the SAT II in math and got a 730, which is a pretty good score. But the report said that this placed her in the 69th percentile, which means that 30% of the people who took the test scored better than that.

Now, I’m no expert on the subject tests, but I was pretty sure that they were centered at 500. If that’s the case, how could this happen?

[Iacob_Matthew]

Note- IANA expert in this field, or any others, for that matter.

Theoretically, yes.

But, with SAT II’s, people tend to score so far out of whack that it’s almost impossible to average it that way. I got an 800 on the Math IIC, and was in the 52nd percentile. If 48% of test takers get it perfect, adjusting that to be 500-centric is almost impossible.

Also,

@http://www.straightdope.com/classics/a1_385.html

The idea behind the present SAT scoring system is that scaled scores should be equivalent from one year to the next–in other words, so that getting a 650 in the verbal section requires the same amount of brainpower in 1997 as it took in 1965. The problem, obviously, is that the difficulty of the tests fluctuates from year to year, as does the caliber of the test-taking population.

…

Finally, I should point out that even if somebody did get a score ten points higher than yours, the difference is statistically meaningless. ETS states that only scoring differences in excess of 65 points indicate a genuine difference in ability.

Your sister’s 730 might be a difference of one question from an 800, and some people will guess on a few and still get everything right, meaning that there is no actual difference in their mathematical abilities. To average it out (percentile-wise), she would have gotten around 600 for having one unlucky guess, which would be flat-out unfair and would be misleading as to her ability.

[Shagnasty]

Math and quantitative scores on the SAT do not follow the bell curve. They are not normally distributed What you will see on most tests is that scores will be normally distributed. Quantitative and Math subtests show a piling at the high end that refect a lot of people can get a perfect or near perfect score. Those that score lower than that will see that their percentile score is much lower that they would have gotten in say a verbal section.

[Chronos]

Doesn’t that indicate, then, that those subject tests are far too easy? If half your testing population can get a perfect score, then you’re getting mighty close to the point where the test doesn’t tell you anything at all.

[iwakura43]

Chronos, I think, in the view of the test makers, those kids who have scored 800 have showed mastery of the subject. The Math IIC also has to have some sort of equivalence to the other SAT IIs–it would not be fair to compare a very, very difficult (hypothetical) Math test score to a comparatively easy SAT II English score, as college admissions officers would be wont to do.

/also got 800 on the IIc. Fat lot of good it’s done me, too.