Suppose observed data are [[文件:Wiki-IPWE-Figure1.png]] <nowiki><math>\{\bigl(X_i,A_i,Y_i\bigr)\}^{n}_{i=1}</math></nowiki> drawn i.i.d (independent and identically distributed) from unknown distribution P, where | Suppose observed data are [[文件:Wiki-IPWE-Figure1.png]] <nowiki><math>\{\bigl(X_i,A_i,Y_i\bigr)\}^{n}_{i=1}</math></nowiki> drawn i.i.d (independent and identically distributed) from unknown distribution P, where |