Just as the regression calculations provide an estimate of the mean value of the dependent variable, the phenotype, at each central age, they correspondingly provide a parameter estimate (β) for the each of the covariates in the regression model. The parameter estimates are transformed into effect sizes by rescaling them in terms of the standard deviation of the dependent variable values. The use of effect sizes (and their corresponding p-values) from the regression calculations provides a sequence of association estimates spaced at 1/10th year intervals over ages 12 to 25. In this method, association is a function of age specified by a sequence of values, not by a functional form. Compared to using separate non-overlapping age ranges, the use of the local linear regression method provides greater power from the use of more observations for each parameter estimate and greater temporal resolution while resulting in the smoothing of estimates and a more complex interpretation of the results. Since there are 4 SNPs and 6 phenotypes (3 scalp locations: Fz, Cz, Pz × 2 modalities: auditory and visual) there are 24
