I am reviewing a dissertation that does a meta-analysis of studies looking at a certain behaviour in rodents.
The author analysed ~20 studies and did a meta-analysis. They then split those studies into sub-categories, depending on the specific methodology that was used in each study (the same thing can be measured in several different ways) and performed one meta-analysis per group.
Finally, they split the original set in a different way (depending on another factor) and performed some further multiple meta-analyses.
I am really not that familiar with meta-analyses, so I am wondering whether this is good practice, or whether they should have included methodology as a factor in their overall analysis instead? If splitting data into multiple subgroups should there be a multiple comparison correction?