% -*- texinfo -*-
% @deftypefn {Function File} {[@var{pval}, @var{z}] =} u_test (@var{x}, @var{y}, @var{alt})
% For two samples @var{x} and @var{y}, perform a Mann-Whitney U-test of
% the null hypothesis PROB (@var{x} > @var{y}) == 1/2 == PROB (@var{x}
% < @var{y}). Under the null, the test statistic @var{z} approximately
% follows a standard normal distribution. Note that this test is
% equivalent to the Wilcoxon rank-sum test.
%
% With the optional argument string @var{alt}, the alternative of
% interest can be selected. If @var{alt} is @code{'~='} or
% @code{'<>'}, the null is tested against the two-sided alternative
% PROB (@var{x} > @var{y}) ~= 1/2. If @var{alt} is @code{'>'}, the
% one-sided alternative PROB (@var{x} > @var{y}) > 1/2 is considered.
% Similarly for @code{'<'}, the one-sided alternative PROB (@var{x} >
% @var{y}) < 1/2 is considered. The default is the two-sided case.
%
% The p-value of the test is returned in @var{pval}.
%
% If no output argument is given, the p-value of the test is displayed.
% @end deftypefn