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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

From: An integrated workplace mental health intervention in a policing context: Protocol for a cluster randomised control trial

  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