Table 2.

Summary of the critical appraisal for included studies

Appraisal question	Yes	No	Unclear	N/A
Is there a clear statement of aims or a clearly defined question?	75 (94%)	5 (6%)	0 (0%)	0 (0%)
Was the methodology employed appropriate to the research question?	47 (59%)	0 (0%)	4 (5%)	29 (36%)
Was the data collection performed appropriately?	70 (88%)	9 (11%)	1 (1%)	0 (0%)
Was the data analysis rigorous?	34 (42%)	5 (6%)	6 (8%)	35 (44%)
Was there a clear statement of results?	72 (90%)	8 (10%)	0 (0%)	0 (0%)
Was the overall relevance to our research question high?	32 (40%)	48 (60%)	0 (0%)	0 (0%)

N/A: not applicable.