Table 6 Power calculations for primary PHQ-9 outcome (response rate at 6 months defined as 50% improvement from baseline)
No. of clusters per group | Cluster size | Proportion responded in control group | Proportion responded in intervention group | Alpha | ICC | Power (No dropout) | Power (20% dropout) |
|---|---|---|---|---|---|---|---|
20 | 50 | 0.30 | 0.40 | 0.05 | 0.04 | 76 | 73 |
20 | 50 | 0.30 | 0.40 | 0.05 | 0.02 | 90 | 87 |
20 | 50 | 0.30 | 0.42 | 0.05 | 0.04 | 89 | 87 |
20 | 50 | 0.30 | 0.42 | 0.05 | 0.02 | 97 | 96 |
20 | 50 | 0.35 | 0.45 | 0.05 | 0.02 | 89 | 87 |
20 | 50 | 0.35 | 0.47 | 0.05 | 0.02 | 97 | 95 |