Bob scores 610 on his SAT's. If the mean score is 580 and the standard deviation is 115, what percentile is Bob's SAT score?
Percentile is percentage ≤ a particular score.
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. Multiply by 100 to get percentage.