Table 3 The use of methods to reduce the risk of selection bias in trials that stratified by site of recruitment
Trials (n = 67) | |
|---|---|
Recruiters blinded? – number (%) | |
No | 1 (1) |
Yes | 1 (1) |
Not stated | 65 (97) |
Randomisation method – number (%) | |
Stratified permuted block | 39 (58) |
Minimisation | 13 (19) |
Other | 3 (4) |
Not stated | 12 (18) |
Block sizes stated? – number (%) | |
No | 16/39 (41) |
Yes | 23/39 (59) |
Were block sizes random? - number (%) | |
No | 16/39 (41) |
Yes | 6/39 (15) |
Not stated | 17/39 (44) |
Largest block size used – median (IQR) | 8 (4 to 11) |
Was minimisation deterministic? – number (%) | |
No | 1/13 (8) |
Yes | 0/13 (0) |
Not stated | 12/13 (92) |
Balanced for prognostic factors? – number (%) | |
No | 27 (40) |
Yes | 40 (60) |
Number of prognostic factors balanced – median (IQR) | 2 (1 to 3) |