Recognizing percentiles

A percentile is the value of a variable below which a certain percent of observations fall. • So the 20th percentile is the value (or score) below

which 20 percent of the observations may be found.

The term percentile and the related term percentile rank are often used in descriptive statistics as well as in the reporting of scores from norm-referenced tests.

How to think about percentiles

Percentiles split a set of ordered data into hundredths.

(Deciles split ordered data into tenths). For example, 70% of the data should fall below the 70th percentile.

Percentiles cluster around the MEDIAN In a symmetrical bell curve, with enough

cases, the median and the mean are equivalent.

Bob has a percentile rank of 84.• What does this look like on a bell curve?

Chris has a percentile rank of 62.• What does this look like on a bell curve?

Jaime has a percentile rank of 89.• What does this look like on a bell curve?

Andy has a percentile rank of 38.• What does this look like on a bell curve?

Charlie has a percentile rank of 11.• What does this look like on a bell curve?

Jackie has a percentile rank of 97.• What does this look like on a bell curve?

Brooke has a percentile rank of 16.• What does this look like on a bell curve?

Jason has a percentile rank of 99.• What does this look like on a bell curve?

Jason has a percentile rank of 99.It might also look like this…