EDIT: I now believe this question was based on misguided information. See my answer.
I'm looking through this meta-analysis (of studies on the effects of mindfulness on healthy individuals) for some personal research.
On page 6 of the document (and in the table on page 7), it gives analysis of heterogeneity 'within-group (pre post analyses)' and 'between group'.
Could you explain what these terms mean, in layman's language?
I understand that in general, heterogeneity between studies included in a meta-analysis means (basically) that the features of the studies included are quite varied (e.g. demographics studied, outcomes measured, measurement criteria used, etc.)
So does heterogeneity between groups mean that... for the subgroups in the metaanalysis, there was a lot of heterogeneity between the studies that contributed data to those subgroups? What about heterogeneity within groups?