Table 7 Percentage of trials re-estimating the sample size, conditional power among trials that re-estimated the sample size and overall mean and median sample size for sample size re-estimation using conditional power
θ | Planned distribution of the prognostic factor | Planned n t | Percent re-estimating sample size | Empirical conditional power | Mean sample size | Median sample size |
|---|---|---|---|---|---|---|
Misspecification of the prognostic factor: 0% | ||||||
5 | 10% | 1,418 | 37.44% | 0.9471 | 2,500 | 1,418 |
20% | 798 | 37.30% | 0.9566 | 1,470 | 798 | |
30% | 608 | 37.74% | 0.9671 | 1,143 | 608 | |
40% | 532 | 38.00% | 0.9689 | 984 | 532 | |
50% | 512 | 39.44% | 0.9660 | 989 | 512 | |
15 | 10% | 178 | 37.44% | 0.9701 | 327 | 178 |
20% | 100 | 40.48% | 0.9674 | 202 | 100 | |
30% | 78 | 39.28% | 0.9695 | 150 | 78 | |
40% | 68 | 42.02% | 0.9719 | 155 | 68 | |
50% | 64 | 43.58% | 0.9748 | 154 | 64 | |
Misspecification of the prognostic factor: -5% | ||||||
5 | 10% | 1,418 | 49.70% | 0.8881 | 3,568 | 1,418 |
20% | 798 | 43.12% | 0.9429 | 1,696 | 798 | |
30% | 608 | 40.98% | 0.9458 | 1,231 | 608 | |
40% | 532 | 38.56% | 0.9570 | 1,062 | 532 | |
50% | 512 | 38.82% | 0.9629 | 987 | 512 | |
15 | 10% | 178 | 45.00% | 0.8738 | 402 | 178 |
20% | 100 | 42.54% | 0.9342 | 219 | 100 | |
30% | 78 | 43.56% | 0.9660 | 171 | 78 | |
40% | 68 | 43.38% | 0.9779 | 153 | 68 | |
50% | 64 | 44.40% | 0.9770 | 155 | 64 | |
Misspecification of the prognostic factor: -15% | ||||||
5 | 10% | 1,418 | -- | -- | -- | -- |
20% | 798 | 51.98% | 0.7618 | 2,425 | 865 | |
30% | 608 | 47.34% | 0.8952 | 1,439 | 608 | |
40% | 532 | 44.96% | 0.9346 | 1,155 | 532 | |
50% | 512 | 41.42% | 0.9546 | 1,028 | 512 | |
15 | 10% | 178 | -- | -- | -- | -- |
20% | 100 | 48.70% | 0.7573 | 267 | 100 | |
30% | 78 | 46.80% | 0.9167 | 190 | 78 | |
40% | 68 | 47.38% | 0.9565 | 161 | 68 | |
50% | 64 | 44.50% | 0.9685 | 148 | 64 | |
Misspecification of the prognostic factor: +5% | ||||||
5 | 10% | 1,418 | 25.94% | 0.9861 | 1,984 | 1,418 |
20% | 798 | 33.26% | 0.9747 | 1,310 | 798 | |
30% | 608 | 35.76% | 0.9676 | 1,096 | 608 | |
40% | 532 | 37.68% | 0.9618 | 975 | 532 | |
50% | 512 | 39.24% | 0.9623 | 969 | 512 | |
15 | 10% | 178 | 28.32% | 0.9845 | 263 | 178 |
20% | 100 | 35.36% | 0.9762 | 177 | 100 | |
30% | 78 | 37.42% | 0.9840 | 153 | 78 | |
40% | 68 | 43.32% | 0.9797 | 150 | 68 | |
50% | 64 | 45.72% | 0.9790 | 157 | 64 | |
Misspecification of the prognostic factor: +15% | ||||||
5 | 10% | 1,418 | 15.04% | 0.9960 | 1,472 | 1,418 |
20% | 798 | 27.34% | 0.9824 | 1,159 | 798 | |
30% | 608 | 34.22% | 0.9673 | 1,007 | 608 | |
40% | 532 | 38.58% | 0.9725 | 1,026 | 532 | |
50% | 512 | 41.56% | 0.9644 | 1,045 | 512 | |
15 | 10% | 178 | 14.40% | 0.9944 | 190 | 89 |
20% | 100 | 30.38% | 0.9888 | 159 | 100 | |
30% | 78 | 37.62% | 0.9856 | 149 | 78 | |
40% | 68 | 43.78% | 0.9753 | 151 | 68 | |
50% | 64 | 48.00% | 0.9708 | 168 | 64 | |