Table 2.

Results of multiple meta-regression to assess the source of heterogeneity

Variables	Coefficient	SE	t	P
Sample size	−0.0004	0.0014	−2.94	0.004
Quality of studies	−0.002	0.003	−0.70	0.484
Year of publication	−0.006	0.003	−0.62	0.540
Location	−0.002	0.006	−0.33	0.745

SE=Standard error