Table 2.
Number of time points | Probabilities | Compound symmetry (CS) within-subject covariance structure and correlation | First-order autocorrelation (AR(1)) within-subject covariance structure and correlation | |||||
---|---|---|---|---|---|---|---|---|
p1 | p2 | ρ = 0.2 | ρ = 0.5 | ρ = 0.8 | ρ = 0.2 | ρ = 0.5 | ρ = 0.8 | |
T = 3 | 0.1 | 0.2 | 152 | 214 | 276 | 140 | 192 | 260 |
0.3 | 52 | 74 | 94 | 48 | 66 | 88 | ||
0.4 | 30 | 42 | 52 | 28 | 38 | 50 | ||
0.5 | 22 | 28 | 36 | 20 | 26 | 34 | ||
0.2 | 0.3 | 224 | 314 | 402 | 206 | 282 | 380 | |
0.4 | 68 | 92 | 118 | 62 | 84 | 112 | ||
0.5 | 34 | 48 | 60 | 32 | 42 | 56 | ||
0.3 | 0.4 | 280 | 386 | 492 | 254 | 348 | 466 | |
0.5 | 76 | 106 | 134 | 70 | 96 | 126 | ||
0.4 | 0.5 | 308 | 424 | 540 | 280 | 382 | 512 | |
T = 6 | 0.1 | 0.2 | 110 | 188 | 264 | 76 | 122 | 206 |
0.3 | 40 | 64 | 90 | 28 | 42 | 70 | ||
0.4 | 24 | 38 | 52 | 16 | 26 | 40 | ||
0.5 | 22 | 26 | 34 | 12 | 18 | 28 | ||
0.2 | 0.3 | 166 | 276 | 386 | 114 | 180 | 302 | |
0.4 | 50 | 82 | 114 | 34 | 54 | 88 | ||
0.5 | 26 | 42 | 58 | 18 | 28 | 46 | ||
0.3 | 0.4 | 208 | 342 | 474 | 140 | 222 | 370 | |
0.5 | 58 | 94 | 130 | 40 | 62 | 102 | ||
0.4 | 0.5 | 230 | 376 | 520 | 156 | 244 | 406 |
Estimates are for the minimum total sample required in two groups, with a sample allocation ratio of 1:1, for comparison of event probabilities p1 and p1 assumed to be constant over time, with use of the logit link for various values T, p1, p1, and ρ. Estimates shown are for setting the random effects to G = 1, type I error to 0.05, and type II error to 0.20.