The paired sample WilCoxon sign rank test can be used to test whether the median of the first population is the same as that of the second population, which the two populations are matched with equal size.
The value of can be used to perform a significance test on the median against the alternative hypothesis. Let be the size of significance test (that is, is the probability of rejecting when is true). If then the null hypothesis should be rejected. Typically might be 0.05 or 0.01.
For more details of the algorithm, please refer to nag_wilcoxon_test (g08agc)