Hi everyone,

I have a sample of 166 bonds (i.e. n=166). I have broken these down into subsamples based on some characteristics of the bonds, ending up with 8 subsamples (these are not mutually exclusive) based on three dummy variables.

For each of these subsamples, I want to test if the dependent variable (Yield) is significantly different from zero. I have run Shapiro Wilks and for 6 of the 8 subsamples I reject the normality hypothesis. From my understanding the Wilcoxon rank sum/Mann Whitney U-test is only used to test if the means from two samples are significantly different from each other. However, I only have one sample (i.e. each subsample), and I want to test if that subsample's mean is significantly different form zero. How do I go about doing this? For the two subsamples where I don't reject normality, should I run a one sample t test or should I use a non-parametric test for all subsamples?

Best,

Nils