In descriptive statistics, a percentile is any of the 99 values that divide the values in a set of data into 100 equal parts, so that each part represents 1/100th of the sample or population.
Some percentiles have special names:
The 10th, 20th, ... 90th percentiles are called deciles.
The 25th, 50th, and 75th percentiles are called quartiles.
