To further examine the different effects for each SNP among college graduates and for those without a college degree, we estimated comparable GWAS models separately for the two groups. Given the reduced sample size, we do not expect p values to exceed the genome-wide significance criteria. The parameter estimates and p values for college graduates and non–college graduates are plotted against one another in Fig. 4. The figure includes any SNP that had a p value of 10–3 (p < .001) or lower for either group. This value is much weaker than the traditional level of genome-wide significance, but it provides a reasonable threshold for us to examine the distribution of these parameter estimates and corresponding p values for the two groups. The vertical and horizontal lines in the panels on the left denote estimates with a magnitude of 2. As an example, consider the SNP in zone 2 of the upper-left panel that is indicated by the dark circle. This is an example of a SNP that is associated with BMI for those with a college degree but not for those without a college degree.
