In some studies a combination of factors were presented for aggregation
(e.g., multiple groups, time-points, and measures), which required systematic
application of the aggregation strategies described. Once computed, a sensitivity
analysis of aggregated effects was conducted by regressing effect size onto
the number of groups, time-points, and measures aggregated in a fixedweighted
analysis. This analysis revealed no systematic biasing (rmax = .10).
Thus, having applied these selection and estimation procedures systematically,
we calculated a pool of independent effect sizes (N = 51) for meta-analysis.