Table 3 Limitations of specific studies

Recruitment method not reported

1 [59]

Failed to report response rate

12 [20, 33, 34, 36,37,38,39, 48,49,50, 59, 63]

Response rate reported as ‘low’

1 [41]

Response rate less than 40%

7 [21, 26, 43, 58, 62, 64, 65]

Explicitly informed participants of the purpose of the study

7 [25, 27, 32, 42, 58, 60, 67]

Gave participants tests or questionnaires that indicated patient characteristic under scrutiny prior to vignette

2 [48, 49]

Did not specify whether they informed participants about the purpose of the study

16 [22, 24, 28,29,30,35,31, 34,35,36, 39, 44, 59, 61, 62, 64, 66]

Small sample size

3 [20, 21, 48]

Failed to report calculating power when designing study

All studies failed except the 15 referenced here that did [27,28,29,30,31,32,33,34,35,36, 39, 40, 42, 43, 59]

Full information on statistical methods used not provided

4 [32, 49, 61, 63]