aggregation bias (Thompson & Higgins, 2002). In meta-
regression, it is important to not assume that a statistical relation-
ship between group-level variables necessarily mirrors that be-
tween corresponding individual-level variables; in fact, in many
cases, this assumption is quite incorrect. Likewise, the meta-
regression findings presented in this article should be viewed with
the same degree of caution; future research can make more defin-
itive associative conclusions using individual- and group-level
data, as others have argued (Reade, Delaney, Bailey, & Angus,
2008).