In fact, the full model in Forbes’ paper has a few more variables and looks like the diagram in Figure 4.7. Note that Game 5 is embedded in this model in the sense that the variables A, B, C, X, and Y have exactly the same relationships. So we can transfer our conclusions over and conclude that we have to control for A and B or for C; but C is an unobservable and therefore uncontrollable variable. In addition we have four new confounding variables: D = parental asthma, E = chronic bronchitis, F = sex, and G = socioeconomic status. The reader might enjoy figuring out that we must control for E,
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