Table 3 Sample sizes for various combinations of baseline (p) and follow-up (r) measures. Correlations for pre, post and mix are 0.7, 0.7 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% | 94% | 92% | 90% | 89% | 89% | 88% | 88% | 88% | 88% | 87% | 87% |
2 | 80% | 74% | 72% | 70% | 69% | 69% | 68% | 68% | 68% | 68% | 67% | 67% |
3 | 73% | 67% | 65% | 64% | 63% | 62% | 62% | 61% | 61% | 61% | 61% | 60% |
4 | 70% | 64% | 62% | 60% | 59% | 59% | 58% | 58% | 58% | 58% | 57% | 57% |
5 | 68% | 62% | 60% | 58% | 57% | 57% | 56% | 56% | 56% | 56% | 55% | 55% |
6 | 67% | 61% | 58% | 57% | 56% | 56% | 55% | 55% | 55% | 54% | 54% | 54% |
7 | 66% | 60% | 57% | 56% | 55% | 55% | 54% | 54% | 54% | 53% | 53% | 53% |
8 | 65% | 59% | 57% | 55% | 54% | 54% | 53% | 53% | 53% | 53% | 52% | 52% |
9 | 64% | 59% | 56% | 55% | 54% | 53% | 53% | 53% | 52% | 52% | 52% | 51% |
10 | 64% | 58% | 56% | 54% | 53% | 53% | 52% | 52% | 52% | 52% | 51% | 51% |
12 | 63% | 57% | 55% | 54% | 53% | 52% | 52% | 51% | 51% | 51% | 51% | 50% |
15 | 63% | 57% | 54% | 53% | 52% | 52% | 51% | 51% | 51% | 50% | 50% | 50% |