Australian Water Information Dictionary
A set of data arranged in order with values that partition the data into three groups, each containing one-third of the total data. To define these terciles, the historical data is arranged in order from lowest to highest and then the data is partitioned into three groups. The lowest third of the data values are defined as the lowest tercile, the middle third of the values are the middle tercile and the upper third of the values are the upper tercile.
For example, if you had 100 data values the lowest tercile would contain the 1st–33rd data values, the middle tercile the 34th–67th values and the upper tercile the 68th–100th values.
This definition applies to: