For each of the five SNPs an analysis was run with the ERO measure taken from each of the three leads, as described in section 2.4 for a total of fifteen models. An examination of the logistic regression results showed that for each SNP, the beta coefficients had little difference when different leads were used; similarly, for each ERO measure the beta coefficients had little difference when different SNPs used. The same was true of coefficients for the clinical variables. We conclude that the effect of each covariate is essentially independent of the effect of any of the others. Thus results from SNPs, electrophysiological variables, and other variables can be reported seriatim without any distortion. Applying the Nyholt correction (Nyholt, 2004) derived from the LD matrix, we obtain 3.2 effective SNPs. The independence of the covariates also implies that the effective number of tests is no more than the number of age ranges times the sum of the effective number of SNPs and electrophysiological variables in each sample group. Considering that the overall pattern of results is of primary interest,
