These are examples that have been worked out by creating FreeSurfer Grou Descriptor (FSGD) files and contrasts for testing various hypotheses. These are not meant to be exhaustive, nor is it meant to teach you statistics. See these slides for more of the statistics background on group analysis and how it applies to FreeSurfer. An alternative to constructing your own FSGD files is to use QDEC, though QDEC cannot be used with more than four groups and/or more than two continuous variables.