The Median test is a special case of the chi-square test with fixed marginal totals. It tests whether several samples came from populations with the same median. The null hypothesis is that all samples have the same median.
- the data are either importantly non-normally distributed
- the measurement scale of the dependent variable is ordinal (not interval or ratio)
- or the data sample is too small.
Given k independent samples of numeric values, a Median test is produced for each set of unique values of the group-by variables (GBVs), if any, testing whether all the populations have the same median. Output for each set of unique values of the GBVs is a p-value, which when compared to the user’s threshold, determines whether the null hypothesis should be rejected for the unique set of values of the GBVs. For more than 2 samples, this is sometimes called the Brown-Mood test.