Table 7.

Examples of sample sizes required to have 80% power to attain significant association (family-wide error of 0.05) when using 'LD-adjusted' and unadjusted Bonferroni-corrected significance thresholds in CEU and YRI under different genetic models

P-value	Population	Genotype Relative Risk Aa/AA	Sample Size
3.04 × 10-07	CEU HapMap LD adjusted	1.4	5270 (-890)
2.08 × 10-08	CEU HapMap	1.4	6160
3.04 × 10-07	CEU HapMap LD adjusted	1.6	2550 (-431)
2.08 × 10-08	CEU HapMap	1.6	2981
1.73 × 10-07	YRI HapMap LD adjusted	1.4	5457 (-742)
1.85 × 10-08	YRI HapMap	1.4	6199
1.73 × 10-07	YRI HapMap LD adjusted	1.6	2641 (-358)
1.85 × 10-08	YRI HapMap	1.6	2999

Sample size is calculated with a high risk allele frequency of 10%, disease prevalence of 20%, and power of 0.80, with a difference in allele frequency between the causal marker and the genotyped marker of 10% (D' = 1.0). Sample size indicates the number of cases required (an equal number of controls is also required). The number in parentheses for sample size indicates the difference between the sample size required when using the LD adjusted Bonferroni correction versus using the unadjusted Bonferroni correction (which corrects for 2.4 million CEU HapMap SNPs and 2.7 million YRI HapMap SNPs.