Table 6.
This table shows the minimum sample size required in each group to achieve the given power for detecting the respective effect size when the level of significance is α = 0.05 in all cases. This is for a two-sided two-sample t-test when the population standard deviation in both groups is roughly the same.
| Effect Size = (µ1 − µ2)/σ | Sample Size in Each Group (Power = 0.70) |
Sample Size in Each Group (Power = 0.80) |
Sample Size in Each Group (Power = 0.90) |
|---|---|---|---|
| 0.05 | 4938 | 6280 | 8406 |
| 0.10 | 1235 | 1570 | 2102 |
| 0.15 | 549 | 698 | 934 |
| 0.20 | 309 | 393 | 526 |
| 0.25 | 198 | 252 | 337 |
| 0.30 | 138 | 175 | 234 |