Performing a Mann-Whitney test of a numeric column’s median across two categories

A Mann-Whitney test indicates whether a numeric column’s values appear to be larger in one of two categories. If the values are drawn from distributions having the same shape but different locations across categories, the Mann-Whitney test can be interpreted as a test of whether the group medians are equal.

To perform a Mann-Whitney test:

  1. In the Summary view, use the confidence slider to choose a desired confidence level
  2. Choose the numeric column of interest on the left
  3. Choose a category column that takes two values in the Covariate table
  4. Click the button labeled Boxes below the Covariate view
  5. The result of the Mann-Whitney test will appear in the Bottom Line

Note that even if the observed medians are equal across categories, the Mann-Whitney test can indicate that the population medians are not equal. This is most likely due to the distribution of values differing across categories.

To analyze differences in a numeric column’s median across three or more categories, use a Kruskal-Wallis test.

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