Percentiles and Percentile Ranks

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Percentile (Point)
Formal Definition: A point on the measurement scale below which a specified percentage of the cases in a distribution falls.

It can be thought of as a cut-off point to separate scores. Let's say you want to know how many people in a class failed their test. Then you would use the percentile of 59 (I think that's the grade of an 'F') and find out the percentage of scores that fell below that point.

Calculating percentiles is not fun.

Percentile Rank
Formal Definition: The percentage of cases in a distribution that falls below a given point on the measurement scale.

This tells you how many scores fall below a given score. So if you want to know how well you did on a test compared to your classmates, you would use the percentile rank to see how you rank among your peers.

Calculating percentile ranks is not as bad as percentile points.