Table 2 Marginal decrease in sample size for increasing the number of measures given various correlations between measures. The table refers to the case where no baseline measures are taken.
From: How many repeated measures in repeated measures designs? Statistical issues for comparative trials
| Â | Correlation | ||||||
Measures | 0 | 0.15 | 0.35 | 0.5 | 0.65 | 0.85 | 1 |
2 | -50.0% | -42.5% | -32.5% | -25.0% | -17.5% | -7.5% | 0% |
3 | -16.7% | -14.2% | -10.8% | -8.3% | -5.8% | -2.5% | 0% |
4 | -8.3% | -7.1% | -5.4% | -4.2% | -2.9% | -1.3% | 0% |
5 | -5.0% | -4.3% | -3.3% | -2.5% | -1.8% | -0.8% | 0% |
6 | -3.3% | -2.8% | -2.2% | -1.7% | -1.2% | -0.5% | 0% |
7 | -2.4% | -2.0% | -1.5% | -1.2% | -0.8% | -0.4% | 0% |
8 | -1.8% | -1.5% | -1.2% | -0.9% | -0.6% | -0.3% | 0% |
9 | -1.4% | -1.2% | -0.9% | -0.7% | -0.5% | -0.2% | 0% |
10 | -1.1% | -0.9% | -0.7% | -0.6% | -0.4% | -0.2% | 0% |
11 | -0.9% | -0.8% | -0.6% | -0.5% | -0.3% | -0.1% | 0% |
15 | -0.5% | -0.4% | -0.3% | -0.2% | -0.2% | -0.1% | 0% |