From Glossary of Meteorology


One of a set of numbers (a quantile) on the random-variable axis that divides a probability distribution into four equal areas.

The three quartile points that lie between the extremes of the distribution are designated as Q1, Q2, Q3 and are defined in terms of the distribution function F(x) as follows:
Thus, Q2 coincides with the median. In empirical relative frequency tables, the quartiles are estimated by interpolation. The interquartile range 2Q is the distance from Q1 to Q3; half of this distance Q is called the semi-interquartile range (or quartile deviation) and is sometimes used as a crude measure of variability or spread.

Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.