TABLE 3.

Subgroup analysis.

Study features	Effect size and 95% confidence interval					Test of heterogeneity
	Number of studies	Point estimate	Standard error	Lower limit	Upper limit	Q-value	df (Q)	P-value
Overall effect size
Random	20	0.11	0.02	0.06	0.16	60.64	19	0.00
By publication
Published	15	0.12	0.03	0.06	0.17
Unpublished	5	0.07	0.05	–0.03	0.17
Total between	20					0.62	1	0.43
By type
Universal	19	0.10	0.03	0.06	0.15
Targeted	5	0.17	0.10	–0.02	0.36
Total between	24					0.44	1	0.51
By study design
QED	8	0.20	0.05	0.10	0.30
RCT	12	0.07	0.02	0.02	0.12
Total between	20					5.46	1	0.02
By sample size
Small (≤1000)	13	0.17	0.03	0.12	0.23
Large (>1000)	7	0.05	0.03	–0.01	0.10
Total between	20					10.66	1	0.00
By grade level
Preschool	5	0.20	0.05	0.11	0.29
Elementary	15	0.08	0.03	0.03	0.13
Total between	20					5.23	1	0.02
By socioeconomic status
Low	6	0.10	0.02	0.07	0.14
Middle	6	0.13	0.05	0.02	0.23
Mixed	2	0.05	0.12	–0.18	0.28
Unknown	6	0.13	0.05	0.03	0.24
Total between	20					0.63	3	0.89
By duration
One year	10	0.19	0.04	0.11	0.26
More than one year	10	0.06	0.03	0.00	0.11
Total between	20					7.50	1	0.01
By dosage
Standard	8	0.17	0.03	0.10	0.24
Low	10	0.03	0.03	–0.02	0.08
NA	2	0.16	0.05	0.07	0.25
Total between	20					12.78	2	0.00