Table 3. Internal validity of research designs in child maltreatment intervention studies, according to a systematic review of reviews.

Design	All interventions	Home-visiting	Parent education	Sexual abuse prevention
	% (No.) (n = 298)	% (No.) (n = 149)	% (No.) (n = 46)	% (No.) (n = 74)
Randomized controlled	47.0 (140)	59.1 (88)	28.3 (13)	43.2 (32)
Non-randomized controlled	27.5 (82)	21.5 (32)	39.1 (18)	31.1 (23)
No control group	15.1 (45)	10.1 (15)	23.9 (11)	18.9 (14)
Other	3.1 (9)	0.0	6.4 (3)	2.7 (2)
Not clear from report	1.3 (4)	0.7 (1)	2.1 (1)	2.7 (2)
Missing	6 (18)	8.7 (13)	0.0	1.4 (1)