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Principal stratification is a statistical technique used in causal inference when adjusting results for post-treatment covariates. The idea is to identify underlying strata and then compute causal effects only within strata. It is a generalization of the local average treatment effect (LATE).

Principal stratification is a statistical technique used in causal inference when adjusting results for post-treatment covariates. The idea is to identify underlying strata and then compute causal effects only within strata. It is a generalization of the local average treatment effect (LATE).

主成分化是一种统计技术，用于因果推断时，调整结果的后处理协变量。这个想法是确定下面的地层，然后计算因果效应只有在地层。它是对局部平均处理效应(LATE)的概括。

主分层是一种应用于因果推断的统计技术，它根据处置后协变量来调整因果效应。其基本思想是识别潜在的分层结构，然后只计算每一层的因果效应。这就是所谓的局部平均处理效应(LATE)。

==Example==

==Example==

If the researcher knew the stratum for each subject then the researcher could compare outcomes only within the first stratum and estimate a valid causal effect for that population. The researcher does not know this information, however, so modelling assumptions are required to use this approach.

If the researcher knew the stratum for each subject then the researcher could compare outcomes only within the first stratum and estimate a valid causal effect for that population. The researcher does not know this information, however, so modelling assumptions are required to use this approach.

主成分分层的一个例子就是随机对照试验的磨损。使用二元后处理协变量(例如:。磨损)和二元处理(例如:。“治疗”和“控制”)有四个可能的阶层，受试者可以: # 那些总是留在研究中，不管他们被分配了哪种治疗 # 那些总是退出研究，不管他们被分配了哪种治疗 # 那些只有在分配给治疗组时才退出的人 # 那些只有在分配给对照组时才退出的人 # 如果研究人员知道每个受试者的阶层，那么研究人员只能比较第一阶层的结果，并估计出对该人群有效的因果关系。然而，研究人员并不知道这些信息，因此需要模型假设来使用这种方法。

主分层的一个例子是随机对照试验的退出偏移问题。使用处置后的二元协变量(例如：退出)和二元处置变量(例如：“处置”和“对照”) ，受试者可能有四种情形：

 

# 总是留在研究中的受试者，不管他们被分配了哪种治疗；

# 总是会退出研究的受试者，不管他们被分配了哪种治疗 ；

# 只有在分配到处置组时才退出的受试者；

# 只有在分配到对照组时才退出的受试者。

 

Using the principal stratification framework also permits providing bounds for the estimated effect (under different bounding assumptions), which is common in situations with attrition.  

Using the principal stratification framework also permits providing bounds for the estimated effect (under different bounding assumptions), which is common in situations with attrition.  

Using the principal stratification framework also permits providing bounds for the estimated effect (under different bounding assumptions), which is common in situations with attrition.  

Using the principal stratification framework also permits providing bounds for the estimated effect (under different bounding assumptions), which is common in situations with attrition.  

使用主分层框架还允许为估计效应提供界限(在不同的界限假设下) ，这在磨蚀情况下很常见。

使用主分层框架还允许为估计效应提供界限(在不同的界限假设下) ，这在退出偏移的情况下很常见。

In applied evaluation research, principal strata are commonly referred to as "endogenous" strata or "subgroups" and involve specialized methods of analysis for examining the effects of interventions or treatments in the medical and social sciences.

In applied evaluation research, principal strata are commonly referred to as "endogenous" strata or "subgroups" and involve specialized methods of analysis for examining the effects of interventions or treatments in the medical and social sciences.

In applied evaluation research, principal strata are commonly referred to as "endogenous" strata or "subgroups" and involve specialized methods of analysis for examining the effects of interventions or treatments in the medical and social sciences.

In applied evaluation research, principal strata are commonly referred to as "endogenous" strata or "subgroups" and involve specialized methods of analysis for examining the effects of interventions or treatments in the medical and social sciences.

==See also==

==See also==