Q. How to calculate Percentiles?

Ans.

In a large group of standardized test scores we expect the scores to approximate a normal curve. If all scores are translated to z-scores, then given a z-score, we are be able to determine the approximate percentage of people who scored either above or below this z-score. This is called a percentile. For example, if a student scores in the 84th percentile, this means that 84% of those taking the test scored lower than the student (and about 16% had higher scores).