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. Author manuscript; available in PMC: 2010 Jul 29.
Published in final edited form as: Hum Genet. 2008 Sep 11;124(4):357–368. doi: 10.1007/s00439-008-0560-2

Figure 1. Sample sizes required to reach 80% power to detect an association when different number of markers are tested.

Figure 1

The total number of patients (white bars) or case-parent trios (black bars) required to reach a power of 80% are shown. A genetic factor is assumed, with an effect similar to that of the C509T polymorphism of the TGFβ1 gene in CF-associated lung disease: a 0.34 allele frequency acting recessively with an odds ratio of 2 (Drumm et al. 2005). For the patient samples, it is assumed that the phenotype of interest is present in 50% of the individuals and absent in the remaining 50%. For the trio samples, all patients are assumed to have the phenotype. The program Genetic Power Calculator (Purcell et al. 2003) was used with a Bonferroni correction for multiple testing.