by **Lisa** » Sat Aug 08, 2020 6:50 am

Hi, Paul,

thank you for your renewed feedback.

I wonder why jamovi outputs the biserial rank correlation coefficient as effect size for the Wilcoxon Signed Rank Test.

First, because there is hardly any information (as you wrote yourself) on how to interpret it. And to have an effect size of which one does not know how to interpret it makes little sense.

Second, I wonder why jamovi doesn't just output the common effect size r for the Wilcoxon Signed Rank Test.

In the literature (Even in the one you referred to in your last message) you can find everywhere that the biserial rank correlation is performed when a dichotomous variable is present. But if you just want to calculate an are-post comparison using the Wilcocox Signed Rank Test, i.e. if you have a sample that you test at two measuring points and interval-scaled data are available, I don't know why you should calculate/state the biserial rank correlation coefficient here.

Would it not be preferable to output r? I mean for the t-test for dependent samples jamovi also outputs Cohen's d as effect size, so wouldn´t it make sense to do the same for the non-parametric counterpart and output r for the Wilcoxon Signed Rank Test?

I look forward to hearing from you.

Best Wishes,

Lisa