wilcoxon非参数检验是对中位数做的检验，后面的没有听明白啊？

2# 张智学
你好，我是做的两个样本的检验，两个样本的该变量中位数都为0，为什么用wilcoxon检验，还有显著差异呢，

STATA中的说明：

ranksum tests the hypothesis that two independent samples (i.e., unmatched data) are from populations with the same distribution by using the Wilcoxon rank-sum test, which is also known as the Mann-Whitney two-sample statistic (Wilcoxon 1945; Mann and Whitney 1947).

median performs a nonparametric K-sample test on the equality of medians.  It tests the null hypothesis that the K samples were drawn from populations with the same median.  For two samples, the chi-squared test statistic is computed both with and without a continuity correction.

ranksum and median are for use with unmatched data.

若检验两总体的中位数是否相等，不能只看它们的样本中位数的观测值是否相等。

版主你好，我想问下什么时候用ranksum命令或者median命令呢？这两者的区别没看太懂。现在我想比较两组样本（将总体分成了两部分）的中位数是否存在差异要用哪个命令呢？