Explanation:
Step 1
Subtract the mean from your score. For example, if you scored 33 and the mean is 24, you would get a difference of 9.
Step 2
Divide the difference found in Step 1 by the standard deviation of the data to find the z-score, which is the number of standard deviations away from the mean that your score is. For example, if the standard deviation was 4.5, you would have a z-score of 2.
Step 3
Convert the z-score to a percentile using a z-score chart or converter available online (see Resources section). When converting, be sure to use a one-sided test. For example, a z-score of 2 would be in the 98th percentile.