Nonparametric Statistics

Nonparametric methods compare groups or paired measurements using the ranks of your data rather than its raw values and a normal-distribution assumption. They are the safer choice when your data is skewed, contains extreme values, is ordinal rather than truly numeric, or your sample is too small to trust a normality assumption.

Every method here names its exact/asymptotic mode and its tie-handling convention directly, since these choices change the result. A rank-based test on its own describes a difference in distribution, not automatically a difference in mean or median, unless the two groups being compared share a similar shape.