comprised on many smaller teams and their data have already been synthesized (again using fixed effects assumptions), but separate data for these sub-studies are not consistently available. In some cases, the pieces would be even impossible to separate, as for example when the group of cases was composed of many smaller samples recruited from different places, while the control group was more uniformly recruited. By accepting that the sub-studies are sufficiently homogeneous, the estimates of between-study heterogeneity that we present may tend to be even underestimates of the full heterogeneity that may exist in the data.
