The Wilcoxon Rank Sum (WRS) Test is a nonparametric test used to determine compliance with the decision criterion when the contaminant of concern is also in background. It compares the locations of two populations, to determine if one population is shifted with respect to another. The method employed is a sum of ranks comparison which works by ranking the combined data sets and summing the ranks for each contaminant. The sum of the ranks is then compared to significance values based on the decision alpha.

Select Wilcoxon Rank Sum Test from the Statistics menu -> Paired Statistics. SADA presents the following window.

Select the appropriate information for each data set (what do the drop down boxes represent) and press OK. SADA displays the results for the test.