Assuming EPs as risk indicators, we illustrate in Figure 5 one such possible model. This model includes three sets of genetic risk factors (which we assume for simplicity are uncorrelated), two EPs (EP1 and EP2) and one PD. We further assume that the third genetic risk factor affects only PD. The paths from these sets of genes to EPs and PD are identified by path names so that a11 reflects the path from the first risk factor to the first EP, and path aPD2 reflects the path from the second genetic risk factor to PD. Finally, imagine a situation in which paths a12 and a21 are very low. In such a situation, you would expect (at least from a genetic perspective) that the correlation between the scores on EP1 and EP2 would be quite low. However, both could be valuable and complementary from a research perspective. That is, if paths a11 and aPD1 are high, then EP1 will function as a good risk indicator for the first genetic risk factor. If paths a22 and aPD2 are high, then EP2 will
