Table 4 Sample sizes for various combinations of baseline (p) and follow-up (r) measures. Correlations for pre, post and mix are 0.5, 0.5 and 0.5. Results given relative to a trial with a single baseline and follow-up measure.
From: How many repeated measures in repeated measures designs? Statistical issues for comparative trials
| Â | Number of baseline measures (p) | |||||||||||
No. of follow-up measures (r) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 12 | 15 |
1 | 100% | 89% | 83% | 80% | 78% | 76% | 75% | 74% | 73% | 73% | 72% | 71% |
2 | 67% | 56% | 50% | 47% | 44% | 43% | 42% | 41% | 40% | 39% | 38% | 38% |
3 | 56% | 44% | 39% | 36% | 33% | 32% | 31% | 30% | 29% | 28% | 27% | 26% |
4 | 50% | 39% | 33% | 30% | 28% | 26% | 25% | 24% | 23% | 23% | 22% | 21% |
5 | 47% | 36% | 30% | 27% | 24% | 23% | 22% | 21% | 20% | 19% | 18% | 18% |
6 | 44% | 33% | 28% | 24% | 22% | 21% | 19% | 19% | 18% | 17% | 16% | 15% |
7 | 43% | 32% | 26% | 23% | 21% | 19% | 18% | 17% | 16% | 16% | 15% | 14% |
8 | 42% | 31% | 25% | 22% | 19% | 18% | 17% | 16% | 15% | 14% | 13% | 13% |
9 | 41% | 30% | 24% | 21% | 19% | 17% | 16% | 15% | 14% | 13% | 13% | 12% |
10 | 40% | 29% | 23% | 20% | 18% | 16% | 15% | 14% | 13% | 13% | 12% | 11% |
12 | 39% | 28% | 22% | 19% | 17% | 15% | 14% | 13% | 12% | 12% | 11% | 10% |
15 | 38% | 27% | 21% | 18% | 16% | 14% | 13% | 12% | 11% | 11% | 10% | 9% |