[SciPy-Dev] `ranksums` and `mannwhitneyu` deprecation from `scipy.stats`

[Alex Wagner]

Hello all,

The `mannwhitneyu` and `ranksums` functions are to be deprecated in 17.0 with the introduction of the new `mww` function (for Mann-Whitney-Wilcoxon). Details follow.

The `mannwhitneyu` function has been rewritten to include alternative tests (‘two-sided’, ‘less’, ‘greater’) and to do exact p-value computations on small input sets. This function has been renamed `mww` to avoid breaking backwards compatibility of `mannwhitneyu`, while fixing the reported p-value (`mannwhitneyu` claims to report a ‘one-sided p-value', but in fact reports 1/2 the p-value of a two-sided test). In addition, `mww` returns a Bunch object instead of a named tuple to support future additions to the function (see PR <https://github.com/scipy/scipy/pull/4933#issuecomment-108137084>).

The `ranksums` function has been completely subsumed by the `mww` function, and is to be deprecated for this reason.

If there are any objections to deprecating these functions, or the addition of the `mww` function, please voice them here.

Best,
Alex

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