 A tempting lesson to draw from our opening example is that Simpson’s Paradox arises as a result of averaging over the populations of males and females, and that the only way to eliminate it is by ruling out average effects. However, causal heterogeneity does not by itself lead to the  paradox.[5]  Cases with heterogeneous background factors only produce association reversal if the factors are correlated with the causal variable—as demonstrated by  Theorem 1  in  Section 2.2.