Editing Mode (statistics) (section)

===Uniqueness and definedness===

For some [[probability distribution]]s, the expected value may be infinite or undefined, but if defined, it is unique. The mean of a (finite) sample is always defined. The median is the value such that the fractions not exceeding it and not falling below it are each at least 1/2. It is not necessarily unique, but never infinite or totally undefined. For a data sample it is the "halfway" value when the list of values is ordered in increasing value, where usually for a list of even length the numerical average is taken of the two values closest to "halfway". Finally, as said before, the mode is not necessarily unique. Certain [[pathological (mathematics)|pathological]] distributions (for example, the [[Cantor distribution]]) have no defined mode at all.{{Citation needed|date=November 2010}}<ref>{{Cite web |last=Morrison |first=Kent |date=1998-07-23 |title=Random Walks with Decreasing Steps |url=http://www.calpoly.edu/~kmorriso/Research/RandomWalks.pdf |url-status=dead |archive-url=https://web.archive.org/web/20151202055102/http://www.calpoly.edu/~kmorriso/Research/RandomWalks.pdf |archive-date=2015-12-02 |access-date=2007-02-16 |website=Department of Mathematics, California Polytechnic State University}}</ref> For a finite data sample, the mode is one (or more) of the values in the sample.