A student scored in the 85th percentile on her chemistry exam. What does this student's score mean in relation to those of the other test takers?

Answer 1

Technically, because she scored in the 85th percentile, her score was somewhere in the lower 85% of scores, though it may have been very low. All that can be said with certainty is at least 15% of the test takers scored higher than she. To conclude that approximately 15% scored higher and approximately 85% scored lower than she did, it would have to have been said that she scored at the 85th percentile. The Wikipedia page on "percentile" elaborates on this subtle difference in phrasing.

Answer 2

This means that the 85% of the students scored lower on the test, and therefore approximately 15% scored higher. If the number of test-takers is large, then the distinction between "less than" and "less than or equal to" is so small as not to really matter.