| [24] | [6] | [25] | [26] | [29] | [27] | [5] | [28] | |
1 | Selection Bias | 1 | 1 | 3 | 2 | 1 | 1 | 3 | 2 |
2 | Study Design | 3 | 1 | 3 | 3 | 1 | 3 | 3 | 3 |
3 | Control for Confounders | 3 | 2 | 1 | 1 | 1 | 3 | 3 | 3 |
4 | Blinding | 3 | 1 | 3 | 2 | 1 | 3 | 3 | 3 |
5 | Data Collection Methods | 2 | 1 | 1 | 2 | 1 | 2 | 1 | 1 |
6 | Withdrawals and Drop-Outs | 2 | 1 | 3 | 1 | 1 | 2 | 2 | 1 |