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A statistical test based on a [[Rank statistic|rank statistic]]. The Wilcoxon and Mann–Whitney tests (cf. [[Mann–Whitney test|Mann–Whitney test]]; [[Wilcoxon test|Wilcoxon test]]) are examples of rank tests. Rank tests are invariant with respect to groups of transformations defined by continuous strictly-increasing functions. Hence they are invariant with respect to variations of the shift and scaling parameters. Moreover, in many problems of hypotheses testing the most-powerful invariant tests can be well approximated by rank tests.

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  J. Hájek,   Z. Sidák,   "Theory of rank tests" , Acad. Press  (1967)</TD></TR><TR><TD valign="top">[2]</TD> <TD valign="top">  E.L. Lehmann,   "Testing statistical hypotheses" , Wiley  (1986)</TD></TR></table>