Australian Water Information Dictionary
One of a series of threshold values that divides a set of ordered data into 100 groups with an equal number of data points in each.
For example, consider a dataset of annual rainfall totals arranged in increasing order. The 20th percentile is a value with 20% of the data below it and 80% above it. The 90th percentile is a value with 90% of the data below it and 10% above it.
This definition applies to: