[Freesurfer] statistical designs

Hello, group I want to learn more about designs of the general linear models for different statistical tests, such as paired T, ANOVA, and correlation tests. Could anybody suggest some examples of the designs for each model? I am facing a few problems of correlation analysis. If I want to do the within group correlation analysis, how can I do it without groups (or classes) as a regressor (if I only have one class and assign a 0 for the group in the contrast, does it work)? How can I specify the pearson's or Spearman's correlation in the analysis? How to know I have enough subjects for this correlation analysis?

Thank you in advance,

XIn Wang