I would like to perform some paired t-test by using Wilcoxon tests. I am trying to figure out which one should be the assumptions that I need to make from before. From what I found so far I need to respect the following:
- The two groups need to be independent.
- The differences between the two samples need to be normally distributed.
- The variables need to be measured at either the interval or ratio level of measurement.
My question is what exactly should I do for the two last bullets? Also, should I consider checking the constant variance? Is it also an assumption for paired t-tests?