# Quartile

From Glossary of Meteorology

## quartile

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 Thus,

*Q*_{1},*Q*_{2},*Q*_{3}and are defined in terms of the distribution function*F*(*x*) as follows:*Q*_{2}coincides with the median. In empirical relative frequency tables, the quartiles are estimated by interpolation. The interquartile range 2*Q*is the distance from*Q*_{1}to*Q*_{3}; 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.