Table 2. Results of the Downs and Black Checklist for the present systematic review.

Downs and Black Checklist	n	Mean	SD	Minimum	Median	Maximum
Reporting score (converted)	10	0.97	0.04	0.91	1.00	1.00
External validity score (converted)	10	0.20	0.17	0.00	0.33	0.33
Internal validity and outcome bias score (converted)	10	0.66	0.10	0.57	0.64	0.86
Confounding factors score (converted)	10	0.98	0.05	0.83	1.00	1.00
Power score (converted)	10	0.90	0.32	0.00	1.00	1.00
Overall score (converted)	10	0.81	0.04	0.71	0.82	0.86
Overall Score (original, no conversion)	10	22.70	1.16	20.00	23.00	24.00

Abbreviation: SD, standard deviation.