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===Mann-Whitney U test===

===Mann-Whitney U test===

The Mann-Whitney U test (also known as the Wilcoxon Rank Sum test) is commonly used for the comparison of two groups where the variable of interest is continuous but not normally distributed for at least one group.

The Mann-Whitney U test (also known as the Wilcoxon Rank Sum test) is commonly used for the comparison of two groups where the variable of interest is continuous but not normally distributed for at least one group. The basic concept behind the test is that all observations within each group are combined and then ranked in order of magnitude. These are then reassigned to their original groups, and the sums of the ranks in each groups are calculated and compared (by counting, for each observation in either of the groups, the number of observations in the alternate group which have a lower rank, and summing these together). Alternative methods are available for those cases where this approach would not be feasible.

 

==Comparing a quantitative variable between more than two groups==

==Comparing a quantitative variable between more than two groups==