Kreara

Wilcoxon rank-sum test

The Wilcoxon rank-sum test is a non-parametric analog of the two-sample t-test. It is based on ranks of the data, and is used to compare location parameters, such as the mean or median, between two independent populations without the assumption of normally distributed data.


DATA RNKSM;
INPUT TRT $ PAT SCORE @@;
DATALINES;
SER 2 0 SER 3 2 SER 5 3 SER 6 3
SER 8 -2 SER 10 1 SER 12 3 SER 14 3
SER 16 -1 SER 17 2 SER 20 -3 SER 21 3
SER 22 3 SER 24 0 SER 26 2 SER 27 -1
PBO 1 3 PBO 4 -1 PBO 7 2 PBO 9 3
PBO 11 -2 PBO 13 1 PBO 15 0 PBO 18 -1
PBO 19 -3 PBO 23 -2 PBO 25 1 PBO 28 0
;

PROC NPAR1WAY WILCOXON DATA = RNKSM;
CLASS TRT; VAR SCORE;
TITLE1 'The Wilcoxon Rank-Sum Test';
RUN;