Learn how to complete a Mann–Whitney U test on SPSS and how to report the results in APA style.
Note: the APA symbol for median is Mdn, not Md (like in the example).
Here is the formula for calculating the r value: Z/(√N)
(If there's a minus symbol before your Z value, you can ignore it.)
Here is the formula with the values from the example inputted: 3.22/(√20) = .72
If you copy and paste 3.22/(√20) into Google and replace the Z and N values with your own, you'll be able to calculate your own r value.
According to Cohen (1988), r values above .1 can be described as small, values above .3 can be described as moderate, and values above .5 can be described as large.
Cohen, J.W. (1988). Statistical power analysis for the behavioral sciences (2nd edn). Hillsdale, NJ: Lawrence Erlbaum Associates.