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
Minor allele frequency	GRR sought	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
0.01	2	1900	>300000
0.05	1.5	1300	50000
0.05	2	400	15000
0.2	1.5	600	5000
0.2	2	220	1500
0.4	1.5	750	900
0.4	2	300	350