Table 1 Sample size and power calculations for mental health literacy outcomes evaluated in this randomised controlled trial taking into account the cluster design at Alpha = 0.05 and Power = 0.90
|  | Mean | SD | Effect size (d) | Req’d standard sample size N | ICC | Design effect | Required sample size accounting for cluster design N | Required sample size after allowing for 30 % attrition |
|---|---|---|---|---|---|---|---|---|
Mental health knowledge (n = 423) | 11.14 | 3.57 | 1.79 | 84 | 0.050 | 1.95 | 164 | 234 |
Job control (n = 678) | 49.82 | 11.02 | 8.0 | 40 | 0.032 | 1.60 | 64 | 91 |
Psychological demands (n = 700) | 14.85 | 3.73 | 3.9 | 20 | 0.050 | 1.94 | 39 | 56 |
Colleague social support (n = 712) | 3.07 | 1.23 | 1.2 | 23 | 0.048 | 1.92 | 44 | 63 |
Supervisor social support (n = 710) | 3.10 | 1.38 | 1.4 | 21 | 0.019 | 1.37 | 29 | 41 |