My question is whether I can compare two different effect sizes (Cohen's d and r). I have tested the differences between two paired groups regarding different variables. They are paired because they are measurements at two different time points. One parameter/variable isn't normally distributed and the other is normally distributed, so I did a Wilcoxon signed rank test and a paired t-test (each for different variables). Accordingly, I calculated different effect sizes, r and Cohen's d. What do I have to do to compare the effect sizes? In one parameter it is r = 0.58, in the other d = 0.78. Although d = 0.78 is a medium effect, the median of the second time point differs more clearly from the first time point than for the variable with r = 0.58 (which is a large effect).
Does anyone have any ideas?