(or distribution-free) inferential statistical methods
are mathematical procedures for statistical hypothesis testing
which, unlike parametric statistics
, make no assumptions about the frequency distributions
of the variables being assessed. The most widely used of these methods is probably the chi-square test
. Other widely used non-parametric methods include Mann-Whitney U
, the Kruskal-Wallis one-way analysis of variance, the median test
, Spearman's &rho
, and estimation of probability using the binomial distribution
They may have more statistical power than a parametric test when the assumptions underlying the parametric test are not satisfied.
See also parametric statistics.