In the statistical model used to estimate gender effects the covariates for the intercept are gender, family type (Alcoholic or Community; see section 2.1), and the first two principal components from the stratification analysis of the genetic data from these subjects; the only covariate for the slope is gender. The principal components from the stratification analysis (Astle and Balding, 2009) were used to ensure the greatest comparability with the genotypic model used in a forthcoming study of the trajectories of the association of genetic variants with the theta EROs. Weights for individuals were adjusted to account for multiple observations on single individuals and co-presence of sibs in each of the local linear regression calculations. The bandwidth for the kernel (Epanechnikov) was taken as 0.6 to minimize the mean squared error, although the variation in the size of the error was less than 2% over the range of bandwidths from 0.4 to 0.8.
