From what I read on permutation test, the null hypothesis is usually that there is no difference between the two groups.
I want to test if the difference between the mean of the two groups is $\theta$ ($H_0 : \mu_2 - \mu_1 = \theta$). Can I use a permutation test for that? How could I do it?
I figured that if my null is ''Group A average is 4 units higher than group B average'', maybe I could substract 4 from all values in Group A and then my null would become that there is no difference between the two groups?
My feeling is that I should use another method (maybe bootstrapping) but I am really not sure.
Small precision : my data does not follow normal distribution so that's why I am looking at resampling techniques.