Table 3.
Modified Downs and Black Quality Index results for each study
| Authors, date | Reporting | External validity | Internal validity – bias | Internal validity – confounding | Power | Total (max. 28) | Total % | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | |||
| Healy et al., 2012 [6] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 0 | 1 | 1 | U | 1 | U | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | U | 1 | U | 0 | 20 | 71 |
| McCormick et al., 2013 [15] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 1 | 1 | U | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 23 | 82 |
| Rao et al., 2009 [16] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 0 | 1 | 1 | U | 1 | U | U | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | U | 1 | U | 0 | 20 | 71 |
| Rogers et al., 2006 [17] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 1 | 1 | U | 1 | U | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 21 | 75 |
| Tong & Ng, 2010 [18] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 1 | 1 | U | 1 | U | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 21 | 75 |
0 = No, 1 = Yes, U = Unable to be determined (received a score of 0)
For the full criteria of the Modified Downs and Black Quality Index see Additional file 1