ranksum
              Wilcoxon rank sum test for equal medians. This test is equivalent to a Mann-Whitney U-test.
 p = ranksum (x, y) returns the p-value of a
 two-sided Wilcoxon rank sum test.  It tests the null hypothesis that two
 independent samples, in the vectors X and Y, come from continuous
 distributions with equal medians, against the alternative hypothesis that
 they are not.  x and y can have different lengths and the test
 assumes that they are independent.
 ranksum treats NaN in x, y as missing values.
 The two-sided p-value is computed by doubling the most significant one-sided
 value.
 [p, h] = ranksum (x, y) also returns the
 result of the hypothesis test with h = 1 indicating a rejection
 of the null hypothesis at the default alpha = 0.05 significance level, and
 h = 0 indicating a failure to reject the null hypothesis at the
 same significance level.
 [p, h, stats] = ranksum (x, y) also
 returns the structure stats with information about the test statistic.
 It contains the field ranksum with the value of the rank sum test
 statistic and if computed with the "approximate" method it also contains the
 value of the z-statistic in the field zval.
 […] = ranksum (x, y, alpha) or alternatively
 […] = ranksum (x, y, "alpha", alpha) returns
 the result of the hypothesis test performed at the significance level ALPHA.
 […] = ranksum (x, y, "method", M) defines the
 computation method of the p-value specified in M, which can be "exact",
 "approximate", or "oldexact". M must be a single string.  When "method"
 is unspecified, the default is: "exact" when
 min (length (x), length (y)) < 10 and
 length (x) + length (y) < 10, otherwise the "approximate"
 method is used.
 […] = ranksum (x, y, "tail", tail) defines the
 type of test, which can be "both", "right", or "left".  tail must be a
 single string.
Note: the rank sum statistic is based on the smaller sample of vectors x and y.
Source Code: ranksum