Before revision:  A complete characterization of the sampling error is obtained without requiring regularization or imposing the missing at random assumption. Under the assumption that potential outcome has a factor structure , we provide a distribution theory for the estimated average and individual treatment effects on the treated .
After revision:  A complete characterization of the sampling error is obtained without requiring regularization or imposing the missing at random . We also consider estimation of average and individual treatment effects on the treated under the assumption that potential outcome has a factor structure , we provide a distribution theory for the estimated average and individual treatment effects on the treated .