Table 1
Suggested population sizes (of cases) required in a case control study seeking the effect size shown for a given minor allele frequency (α = 0.05, power 90%)
| Minor allele frequency | GRR sought | Cases required | |
|---|---|---|---|
| Dominant effect | Recessive effect | ||
| GRR, genotype relative risk. | |||
| The numbers given assume that the same numbers of controls as cases are to be recruited. Exact numbers will depend on the precise hypothesis under test and the method of analysis: numbers required may be substantially greater (for example, where attempts to control for confounders are made). In these instances input from a statistician is advised. | |||
| 0.01 | 1.5 | 5500 | >1000000 |
| 2 | 1900 | >300000 | |
| 0.05 | 1.5 | 1300 | 50000 |
| 2 | 400 | 15000 | |
| 0.2 | 1.5 | 600 | 5000 |
| 2 | 220 | 1500 | |
| 0.4 | 1.5 | 750 | 900 |
| 2 | 300 | 350 | |
