You must provide a complete explanation of how you got your answers. For questions involving data analysis, you must attach an output log of how you estimated your parameter values. 1. In the gures below all four DAGs (a-d), X is a binary treatment variable and Y is the outcome variable, U and V are unobservable. S, Z, X and Y are all observable (in your data). For each DAG, write down all backdoor paths from X to Y and indicate whether they are open or closed. Write down a conditioning strategy that satises the backdoor criterion. If one does not exist, why does it not exist? (a) (1)) U V Z* Y X "Y (c) (d)