Causal Effects of Modified Treatment Policies under Positivity Violations: A Partial Identification Approach
正值性违反下修正处理政策的因果效应:部分识别方法
Modified treatment policies (MTPs) are interventions based on each individual's natural treatment value. We study mean outcomes under MTPs for continuous treatments, including exposure mixtures. Positivity is the standard sufficient condition for identifying these mean outcomes without extrapolation: policy-generated values remain supported given covariates. With multivariate treatments or continuous covariates, treatment--covariate combinations can be sparse or unsupported.…