In the case of Clopidogrel and CYP2C19, typically one might assume that CYPC219 variants G: do not predict whether an individual receives Clopidogrel T; are not associated with any confounders predicting Clopidogrel use and stroke, Y; and only affects stroke risk through their interaction with Clopidogrel. Here, CYP2C19 is linked to Stroke.