Approximate power to detect association between an allelic score indexing a biological exposure and disease.

<p>The model is parameterized in terms of the percentage of variance in the biological intermediate explained by the SNP (σ_G²), the strength of the causal relationship between the biological intermediate (β) and liability of disease, which together determine the amount of variance in disease liability explained by the SNP (σ_L²), and the prevalence of disease. Estimates of power are presented for 2000 cases and 3000 controls (α = 0.05), and for 50000 cases and controls (α = 1.1×10⁻⁷).