Table 1:
Total sample sizes necessary to yield 80% or 90% power to detect a treatment-by-subgroup interaction in parallel group studies
| SES | 80% Power | 90% Power | ||||
|---|---|---|---|---|---|---|
| Subgroup Allocation | ||||||
| 50:50 | 34:66 | 25:75 | 50:50 | 34:66 | 25:75 | |
| Sample Size | ||||||
| 1.0 | 126 | 142 | 170 | 170 | 189 | 226 |
| 0.9 | 157 | 174 | 209 | 209 | 233 | 277 |
| 0.8 | 198 | 220 | 262 | 265 | 295 | 352 |
| 0.7 | 258 | 286 | 342 | 345 | 383 | 458 |
| 0.6 | 350 | 389 | 466 | 469 | 522 | 625 |
| 0.5 | 505 | 561 | 671 | 674 | 751 | 898 |
| 0.4 | 786 | 876 | 1049 | 1053 | 1172 | 1402 |
| 0.3 | 1397 | 1557 | 1861 | 1869 | 2083 | 2493 |
SES = Difference in standardized effect size between subgroups