What does "MeanRank" mean in Mannwhitney U, SPSS?

Mann Whitney is a test used when you want to determine whether there is a statistically significant difference in scores for two variables measured at the ordinal level. Since the idea of a "mean" makes little sense for ordinal data, the Mann Whitney procedure is to take all of the scores for the two groups and put them into one column, then rank order them from lowest to highest (or vice versa - I can't remember). Then once the ranks are assigned, the scores are split back into the two groups. Then the mean of the *ranks* in each group is computed, and a test is done to see whether there is a statistically significant difference in the mean ranks for each group. The MeanRank is simply the mean rank score for each group. You can eyeball the mean ranks to see if they are very different across groups - but you really want to look at the p-value - if it is small (less than .05 or .01 or whatever critical value you are using), there is a significant difference between groups.

Mann Whitney U Test Definition

Mann Whitney U Test Spss

example:

A: 1 2 3

B: 2 4 6

MeanRank: A1 A2.5 B2.5 A4 B5 B6

Mean of Rank A= 3.75

Mean of Rank B= 6.75