Table 3

Risk of bias summary for quantitative studies

Study	Study design	Study setting	Selection bias	Performance bias	Attrition bias	Reporting bias	Measurement bias	Analysis
Copp 201719	+	+	+	?	+	+	+	+
McCaffery 201515	+	+	+	?	+	+	+	+
Omer 201314	+	?	+	?	?	+	+	+
Scherer 201317	+	+	+	?	?	+	+	+
Scherer 201525	+	+	+	?	?	+	+	+
Azam 201020	−	+	−	?	?	−	−	−

+ Low risk of bias (done well)
? Unclear or unknown (not reported)
= High risk of bias (not done or done poorly)