Causal Inference, Instrumental Variables, Stats 361, Stanford, Data Science.
Z_i) “Z_i must be relevant, such that Cov[W_i, Z_i]≠0“; Strictly speaking, Z_i must be relevant only to W_i (not to Y_i). “Z_i must satisfy the exclusion restriction, meaning that any effect of Z_ion Y_i must be mediated via W_i”; Again, Z_i must not DIRECTLY affect Y_i 5. Detail of the conditions