Percentile Rank

A percentile rank indicates the percent of the data that is less than a chosen data value.

Percentile rankings are useful when comparing large sets of data. They are often used when comparing

• heights
• weights
• intelligence quotients (IQ)
• test scores

Percentile ranks must be whole numbers and cannot include any fractions or decimals.

For example, if Randall scores in the 90th percentile on a test, 90% of the students who took the test scored lower than Randall. If Joseph scores in the 72nd percentile on a test, 72% of the students who took the test scored lower than Joseph.
 

Example 2

A one-month-old baby girl weighs 3.45 kg. The doctor indicates that the baby's weight is in the 15th percentile. How does this baby's weight compare to other babies her age?

Solution

Since the baby's weight is in the 15th percentile, the baby weighs more than 15% of all the other one-month-old baby girls. Therefore, 85% of one-month-old baby girls weigh more than the baby shown in the picture.