I have two paired samples following normal distributions N(0, $\sigma_1^2$) and N(0, $\sigma_2^2$). Samples represent estimation errors (residuals) of two linear regression models used to predict the same response variable using two different methods/independent variables. I have 30 pairs of residuals, so I would like to apply Wilcoxon signed-rank test to check whether means of absolute values or relative errors are different. Since absolute values do not follow normal distribution, I cannot use t-test or something similar.
I would like to find type II error and statistic power of Wilcoxon signed-rank test. Is there some R function (or any other tool) that can be used? I have found a number of functions for testing the power of tests here http://www.statmethods.net/stats/power.html but I’m not sure could they be applied on Wilcoxon signed-rank test. If there is no built-in function is there some other tool or algorithm to manually calculate error?