Skip to main content

Advertisement

Table 4 Empirical type I error and percentage of trials switching to the quota sampling scheme for the modified quota sampling method

From: Impact of misspecifying the distribution of a prognostic factor on power and sample size for testing treatment interactions in clinical trials

θ Planned distribution of the prognostic factor Planned n t Empirical type I error Percent of trials switching to quota sampling
Misspecification of the prognostic factor: -5%
0 10% 1,418 0.0528 99.90%
20% 798 0.0506 74.26%
30% 608 0.0498 47.34%
40% 532 0.0480 36.66%
50% 512 0.0492 36.06%
0 10% 178 0.0566 34.74%
20% 100 0.0496 12.12%
30% 78 0.0528 11.24%
40% 68 0.0452 11.30%
50% 64 0.0522 8.80%
Misspecification of the prognostic factor: -15%
0 10% 1,418 -- --
20% 798 0.0500 100.00%
30% 608 0.0496 100.00%
40% 532 0.0518 99.92%
50% 512 0.0568 99.76%
0 10% 178 -- --
20% 100 0.0578 89.60%
30% 78 0.0522 62.82%
40% 68 0.0542 50.56%
50% 64 0.0478 41.20%
Misspecification of the prognostic factor: +5%
0 10% 1,418 0.0568 98.68%
20% 798 0.0490 68.74%
30% 608 0.0490 48.10%
40% 532 0.0508 36.48%
50% 512 0.0508 36.64%
0 10% 178 0.0504 34.46%
20% 100 0.0534 16.32%
30% 78 0.0496 10.90%
40% 68 0.0450 8.50%
50% 64 0.0502 8.94%
Misspecification of the prognostic factor: +15%
0 10% 1,418 0.0462 100.00%
20% 798 0.0490 100.00%
30% 608 0.0484 100.00%
40% 532 0.0516 99.76%
50% 512 0.0522 99.86%
0 10% 178 0.0452 97.48%
20% 100 0.0444 70.72%
30% 78 0.0526 51.00%
40% 68 0.0524 38.60%
50% 64 0.0528 40.72%
  1. The margin of error based on the 99% confidence interval is 0.008.