Table 5 Sample sizes for various combinations of baseline (p) and follow-up (r) measures. Correlations for pre, post and mix are 0.9, 0.9 and 0.8. 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% | 91% | 87% | 86% | 85% | 84% | 83% | 83% | 83% | 82% | 82% | 82% |
2 | 86% | 77% | 73% | 72% | 71% | 70% | 69% | 69% | 69% | 69% | 68% | 68% |
3 | 81% | 72% | 69% | 67% | 66% | 65% | 65% | 64% | 64% | 64% | 64% | 63% |
4 | 79% | 70% | 66% | 65% | 64% | 63% | 63% | 62% | 62% | 62% | 61% | 61% |
5 | 78% | 68% | 65% | 63% | 62% | 62% | 61% | 61% | 60% | 60% | 60% | 59% |
6 | 77% | 67% | 64% | 62% | 61% | 61% | 60% | 60% | 60% | 59% | 59% | 59% |
7 | 76% | 67% | 63% | 62% | 61% | 60% | 60% | 59% | 59% | 59% | 58% | 58% |
8 | 76% | 66% | 63% | 61% | 60% | 60% | 59% | 59% | 58% | 58% | 58% | 57% |
9 | 75% | 66% | 63% | 61% | 60% | 59% | 59% | 58% | 58% | 58% | 57% | 57% |
10 | 75% | 66% | 62% | 61% | 60% | 59% | 58% | 58% | 58% | 57% | 57% | 57% |
12 | 75% | 65% | 62% | 60% | 59% | 58% | 58% | 57% | 57% | 57% | 57% | 56% |
15 | 74% | 65% | 61% | 60% | 59% | 58% | 57% | 57% | 57% | 56% | 56% | 56% |