when to use a permutation test how to tell what the difference between a permutation test and t test why is the permutation test compared to the t test how to find out if the data is skewy how does t test on skewed data how to compare p value with permutation test what p value is welch test how to test p value on skewed data average of x mean y when t-testing the difference in mean and standard deviation why is the difference of the means not equal why is it so difficult to test a permutation test t tests for skewed mean what is the p value for permutation test why is x and y based on the t-test what is the confidence interval in a permutation test how to get permutation test results r permutation test for skewed data what is the confidence interval for a welch test? what is the p value of r t test