Editing Median (section)

==Definition and notation==
Formally, a median of a [[Population (statistics)|population]] is any value such that at least half of the population is less than or equal to the proposed median and at least half is greater than or equal to the proposed median. As seen above, medians may not be unique. If each set contains more than half the population, then some of the population is exactly equal to the unique median.

The median is well-defined for any [[Weak ordering|ordered]] (one-dimensional) data and is independent of any [[distance metric]]. The median can thus be applied to school classes which are ranked but not numerical (e.g. working out a median grade when student test scores are graded from F to A), although the result might be halfway between classes if there is an even number of classes. (For odd number classes, one specific class is determined as the median.)

A [[geometric median]], on the other hand, is defined in any number of dimensions. A related concept, in which the outcome is forced to correspond to a member of the sample, is the [[medoid]].

There is no widely accepted standard notation for the median, but some authors represent the median of a variable ''x'' as med(''x''), ''x͂'',<ref name="Bissell1994">{{cite book|author=Derek Bissell | title=Statistical Methods for Spc and Tqm | url=https://books.google.com/books?id=cTwwtyBX7PAC&pg=PA26 |access-date=25 February 2013|year=1994 |publisher=CRC Press |isbn=978-0-412-39440-9 |pages=26–}}</ref> as ''μ''<sub>1/2</sub>,<ref name="StatisticalMedian" /> or as ''M''.<ref name="Bissell1994"/><ref name="Sheskin2003">{{cite book| author=David J. Sheskin|title=Handbook of Parametric and Nonparametric Statistical Procedures | edition = Third |url=https://books.google.com/books?id=bmwhcJqq01cC&pg=PA7 |access-date=25 February 2013|date=27 August 2003 |publisher=CRC Press|isbn=978-1-4200-3626-8 |page=7}}</ref> In any of these cases, the use of these or other symbols for the median needs to be explicitly defined when they are introduced.

The median is a special case of other [[location parameter|ways of summarizing the typical values associated with a statistical distribution]]: it is the 2nd [[quartile]], 5th [[decile]], and 50th [[percentile]].