【问题】

有时候，对比两组非正态数据需要这个检验。

【方法】

signrank

【例子】

Wilcoxon signed-rank test

http://en.wikipedia.org/wiki/Wilcoxon_signed-rank_test

http://upload.wikimedia.org/wikipedia/en/math/7/9/a/79ac57b9275f4dabb71a5e815554b469.png111: signrank：Wilcoxon配对符号秩检验" /> is the sign function, http://upload.wikimedia.org/wikipedia/en/math/0/c/9/0c9683d28a6603306124663815e847b6.png111: signrank：Wilcoxon配对符号秩检验" /> is the absolute value, and http://upload.wikimedia.org/wikipedia/en/math/6/0/c/60cc9655a5f88e01bc72f76307e01689.png111: signrank：Wilcoxon配对符号秩检验" /> is the rank. Notice that pairs 3 and 9 are tied in absolute value. They would be ranked 1 and 2, so each gets the average of those ranks, 1.5.

http://upload.wikimedia.org/wikipedia/en/math/4/2/7/427524afa4d36b05c840fd4a8842e167.png111: signrank：Wilcoxon配对符号秩检验" />

http://upload.wikimedia.org/wikipedia/en/math/6/7/4/674247ade761d55111cf1df33c348003.png111: signrank：Wilcoxon配对符号秩检验" />

http://upload.wikimedia.org/wikipedia/en/math/6/7/4/674247ade761d55111cf1df33c348003.png111: signrank：Wilcoxon配对符号秩检验" />

另注：

Stata里面的ranktest没有这一步

Exclude pairs with http://upload.wikimedia.org/wikipedia/en/math/7/1/d/71db34b688184238e611e67ec2d98f3a.png111: signrank：Wilcoxon配对符号秩检验" /> . Let http://upload.wikimedia.org/wikipedia/en/math/5/9/5/595cd2d067a202297f42b0cb7a20cce9.png111: signrank：Wilcoxon配对符号秩检验" /> be the reduced sample size。