This may be a simple question but...

I'm doing neuroimaging research and long story short, I am doing what is essentially a correlational analysis wherein my output is a brain's-worth of r-values (so like 15000 voxels worth of r-values). In this particular study I had 3 groups and I want to take these brains worth of r-values and see if they differ across the 3 groups. In normal situations in neuroimaging when you have beta weights you just do a 3-way ANOVA on the beta weights to get an F-value (or a t-value for more specific comparisons) so my default was just to assume I could do the same thing here - a 3 way ANOVA with group as the fixed factor. However I realized I'm not sure performing an ANOVA on r-values is appropriate. Can someone speak to this? If it IS inappropriate, can someone recommend how I could go about testing for differences using these values?

Follow-up question: I also have Z-scored brain maps and ultimately I'd like for the comparisons to be made using the Z-scores. I suppose if using an ANOVA on r-values is inappropriate then using one on the Z'd r-values is also inappropriate but if using an ANOVA is okay with correlation values, I'd assume it's okay with Z'd correlation values as well?

Thanks for any help you can provide.

Lauren