First and most important, you don’t see U (the Smoking Gene) anywhere. This was the whole point. We have successfully deconfounded U even without possessing any data on it. Any statistician of Fisher’s generation would have seen this as an utter miracle. Second, way back in the Introduction I talked about an estimand as a recipe for computing the quantity of interest in a query. Equations 7.1 and 7.2 are the most complicated and interesting estimands that I will show you in this book. The left-hand side represents the query “What is the effect of X on Y?” The right-hand side is the estimand, a
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