Powers to detect the specified percentage reductions in the percentages of high-risk prescribing associated with a variety of intra class correlations (ICC), average practice size, anticipated percentages of high-risk prescribing in the control arm and numbers of practices randomised
| Percentage control (%) | Percentage intervention (%) | Percentage reduction | ICC (%) | Average practice size | Number practices control | Number practices intervention | Power |
|---|---|---|---|---|---|---|---|
| 6.1 | 4.8 | 21 | 1.3 | 700 | 85 | 85 | 0.80 |
| 6.1 | 4.7 | 22 | 1.3 | 700 | 79 | 79 | 0.81 |
| 6.1 | 4.7 | 22 | 1.3 | 700 | 75 | 75 | 0.79 |
| 6.1 | 4.7 | 23 | 1.3 | 700 | 70 | 70 | 0.80 |
| 6.1 | 4.5 | 25 | 1.3 | 700 | 85 | 85 | 0.93 |
| 6.1 | 4.5 | 25 | 1.3 | 700 | 79 | 79 | 0.91 |
| 6.1 | 4.5 | 26 | 1.3 | 700 | 75 | 75 | 0.92 |
| 6.1 | 4.5 | 26 | 1.3 | 700 | 70 | 70 | 0.90 |
| 6.1 | 4.5 | 25 | 1.3 | 700 | 85 | 85 | 0.93 |
| 6.1 | 4.4 | 27 | 1.3 | 700 | 79 | 79 | 0.95 |
| 6.1 | 4.4 | 27 | 1.3 | 700 | 75 | 75 | 0.94 |
| 6.1 | 4.4 | 28 | 1.3 | 700 | 70 | 70 | 0.94 |
| 6.1 | 4.7 | 23 | 1.9 | 700 | 70 | 70 | 0.80 |
| 6.1 | 4.7 | 23 | 1.9 | 700 | 75 | 75 | 0.83 |
| 6.1 | 4.8 | 21 | 1.9 | 700 | 85 | 85 | 0.80 |
| 6.1 | 4.5 | 26 | 1.9 | 700 | 70 | 70 | 0.90 |
| 6.1 | 4.5 | 26 | 1.9 | 700 | 75 | 75 | 0.92 |
| 6.1 | 4.4 | 28 | 1.9 | 700 | 70 | 70 | 0.94 |
| 6.1 | 4.4 | 27 | 1.9 | 700 | 75 | 75 | 0.94 |
| 6.1 | 4.5 | 25 | 1.9 | 700 | 85 | 85 | 0.93 |
| 6.1 | 4.7 | 23 | 1.3 | 600 | 70 | 70 | 0.79 |
| 6.1 | 4.7 | 23 | 1.3 | 600 | 75 | 75 | 0.82 |
| 6.1 | 4.7 | 22 | 1.3 | 600 | 80 | 80 | 0.81 |
| 6.1 | 4.5 | 25 | 1.3 | 600 | 75 | 75 | 0.89 |
| 6.1 | 4.5 | 25 | 1.3 | 600 | 80 | 80 | 0.91 |
| 6.1 | 4.6 | 24 | 1.3 | 600 | 85 | 85 | 0.90 |
| 6.1 | 4.4 | 27 | 1.3 | 600 | 80 | 80 | 0.95 |
| 6.1 | 4.4 | 27 | 1.3 | 600 | 85 | 85 | 0.96 |
| 4.5 | 3.4 | 26 | 1.3 | 700 | 70 | 70 | 0.78 |
| 4.5 | 3.4 | 26 | 1.3 | 700 | 75 | 75 | 0.81 |
| 4.5 | 3.4 | 26 | 1.3 | 700 | 80 | 80 | 0.84 |
| 4.5 | 3.4 | 25 | 1.3 | 700 | 85 | 85 | 0.83 |
| 4.5 | 3.2 | 30 | 1.3 | 700 | 70 | 70 | 0.90 |
| 4.5 | 3.2 | 29 | 1.3 | 700 | 75 | 75 | 0.90 |
| 4.5 | 3.3 | 27 | 1.3 | 700 | 80 | 80 | 0.90 |
| 4.5 | 3.3 | 27 | 1.3 | 700 | 85 | 85 | 0.89 |
| 4.5 | 2.9 | 36 | 1.3 | 700 | 70 | 70 | 0.98 |
| 4.5 | 3.2 | 30 | 1.3 | 700 | 85 | 85 | 0.95 |