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This idea is part of the [[Rubin Causal Model|Rubin Causal Inference Model]], developed by [[Donald Rubin]] in collaboration with [[Paul R. Rosenbaum|Paul Rosenbaum]] in the early 1970s. The exact definition differs between their articles in that period. In one of Rubins articles from 1978 Rubin discuss ''ignorable assignment mechanisms'',<ref name="rubin78">{{cite journal |last1=Rubin |first1=Donald |title=Bayesian Inference for Causal Effects: The Role of Randomization |journal=The Annals of Statistics |date=1978 |volume=6 |issue=1 |pages=34–58|doi=10.1214/aos/1176344064 |doi-access=free }}</ref> which can be understood as the way individuals are assigned to treatment groups is irrelevant for the data analysis, given everything that is recorded about that individual. Later, in 1983 <ref>{{cite journal |last1=Rubin |first1=Donald B. |last2=Rosenbaum |first2=Paul R. |title=The Central Role of the Propensity Score in Observational Studies for Causal Effects |journal=Biometrika |date=1983 |volume=70 |issue=1 |pages=41–55 |doi=10.2307/2335942 |jstor=2335942 |doi-access=free }}</ref> Rubin and Rosenbaum rather define ''strongly ignorable treatment assignment'' which is a stronger condition, mathematically formulated as <math>(r_1,r_0) \perp \!\!\!\perp z \mid v ,\quad 0<\operatorname{pr}(z=1)<1 \quad \forall v</math>, where <math>r_t</math> is a potential outcome given treatment <math>t</math>, <math>v</math> is some covariates and <math>z</math> is the actual treatment.
 
This idea is part of the [[Rubin Causal Model|Rubin Causal Inference Model]], developed by [[Donald Rubin]] in collaboration with [[Paul R. Rosenbaum|Paul Rosenbaum]] in the early 1970s. The exact definition differs between their articles in that period. In one of Rubins articles from 1978 Rubin discuss ''ignorable assignment mechanisms'',<ref name="rubin78">{{cite journal |last1=Rubin |first1=Donald |title=Bayesian Inference for Causal Effects: The Role of Randomization |journal=The Annals of Statistics |date=1978 |volume=6 |issue=1 |pages=34–58|doi=10.1214/aos/1176344064 |doi-access=free }}</ref> which can be understood as the way individuals are assigned to treatment groups is irrelevant for the data analysis, given everything that is recorded about that individual. Later, in 1983 <ref>{{cite journal |last1=Rubin |first1=Donald B. |last2=Rosenbaum |first2=Paul R. |title=The Central Role of the Propensity Score in Observational Studies for Causal Effects |journal=Biometrika |date=1983 |volume=70 |issue=1 |pages=41–55 |doi=10.2307/2335942 |jstor=2335942 |doi-access=free }}</ref> Rubin and Rosenbaum rather define ''strongly ignorable treatment assignment'' which is a stronger condition, mathematically formulated as <math>(r_1,r_0) \perp \!\!\!\perp z \mid v ,\quad 0<\operatorname{pr}(z=1)<1 \quad \forall v</math>, where <math>r_t</math> is a potential outcome given treatment <math>t</math>, <math>v</math> is some covariates and <math>z</math> is the actual treatment.
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这个想法是20世纪70年代早期[[Donald Rubin]]和[[Paul R. Rosenbaum|Paul Rosenbaum]] 合作提出的[[鲁宾因果推理模型]]的一部分。但那时,他们文章中可忽略性的确切定义不同。1978年鲁宾在一篇文章中讨论了''可忽略的分配机制'',<ref name="rubin78">{{cite journal |last1=Rubin |first1=Donald |title=Bayesian Inference for Causal Effects: The Role of Randomization |journal=The Annals of Statistics |date=1978 |volume=6 |issue=1 |pages=34–58|doi=10.1214/aos/1176344064 |doi-access=free }}</ref> 其可理解为将个体分配到处理组的方式与数据分析无关,因为已经记录了有关该个体的所有信息。后来,在 1983 年,Rubin 和 Rosenbaum 更确切地定义了“处理分配的强可忽略性”, <ref>{{cite journal |last1=Rubin |first1=Donald B. |last2=Rosenbaum |first2=Paul R. |title=The Central Role of the Propensity Score in Observational Studies for Causal Effects |journal=Biometrika |date=1983 |volume=70 |issue=1 |pages=41–55 |doi=10.2307/2335942 |jstor=2335942 |doi-access=free }}</ref>,这是一个更强的假设条件,数学公式为<math>(r_1,r_0) \perp \!\!\!\perp z \mid v ,\quad 0<\operatorname{pr}(z=1)<1 \quad \forall v</math>,其中<math>r_t</math>是给定处理状态 <math>t</math>下的潜在结果,<math>v</math> 是协变量,<math>z</math> 是实际的处理结果。
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这个想法是20世纪70年代早期[[Donald Rubin]]和[[Paul R. Rosenbaum|Paul Rosenbaum]] 合作提出的[[鲁宾因果推理模型]]的一部分。但那时,他们文章中可忽略性的确切定义不同。1978年鲁宾在一篇文章中讨论了''可忽略的分配机制'',<ref name="rubin78">{{cite journal |last1=Rubin |first1=Donald |title=Bayesian Inference for Causal Effects: The Role of Randomization |journal=The Annals of Statistics |date=1978 |volume=6 |issue=1 |pages=34–58|doi=10.1214/aos/1176344064 |doi-access=free }}</ref> 其可理解为将个体分配到处理组的方式与数据分析无关,因为已经记录了有关该个体的所有信息。后来,在 1983 年,Rubin 和 Rosenbaum 更确切地定义了“处理分配的强可忽略性”, <ref>{{cite journal |last1=Rubin |first1=Donald B. |last2=Rosenbaum |first2=Paul R. |title=The Central Role of the Propensity Score in Observational Studies for Causal Effects |journal=Biometrika |date=1983 |volume=70 |issue=1 |pages=41–55 |doi=10.2307/2335942 |jstor=2335942 |doi-access=free }}</ref>,这是一个更强的假设条件,数学公式为<math>(r_1,r_0) \perp \!\!\!\perp z \mid v ,\quad 0<\operatorname{pr}(z=1)<1 \quad \forall v</math>,其中<math>r_t</math>是给定处理状态 <math>t</math>下的潜在结果,<math>v</math> 是协变量,<math>z</math> 是实际的处理状态。
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Formally it has been written as [Y<sub>i</sub>1, Y<sub>i</sub>0] ⊥ Tx<sub>i</sub>, or in words the potential Y outcome of person ''i'' had they been treated or not does not depend on whether they have really been (observable) treated or not. We can ignore in other words how people ended up in one vs. the other condition, and treat their potential outcomes as exchangeable. While this seems thick, it becomes clear if we add subscripts for the ‘realized’ and superscripts for the ‘ideal’ (potential) worlds (notation suggested by [https://www.cambridge.org/core/books/statistical-models-and-causal-inference/7CE8D4957FF6E9615AAAC4128FA8246E David Freedman]; a visual can help here: [https://drive.google.com/open?id=1nLHHH0il225LIy33nRiH3ZfgoX1_-_V9 potential outcomes simplified]).
 
Formally it has been written as [Y<sub>i</sub>1, Y<sub>i</sub>0] ⊥ Tx<sub>i</sub>, or in words the potential Y outcome of person ''i'' had they been treated or not does not depend on whether they have really been (observable) treated or not. We can ignore in other words how people ended up in one vs. the other condition, and treat their potential outcomes as exchangeable. While this seems thick, it becomes clear if we add subscripts for the ‘realized’ and superscripts for the ‘ideal’ (potential) worlds (notation suggested by [https://www.cambridge.org/core/books/statistical-models-and-causal-inference/7CE8D4957FF6E9615AAAC4128FA8246E David Freedman]; a visual can help here: [https://drive.google.com/open?id=1nLHHH0il225LIy33nRiH3ZfgoX1_-_V9 potential outcomes simplified]).
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数学形式上,它被写成[Y<sub>i</sub>1, Y<sub>i</sub>0] ⊥ Tx<sub>i</sub> ,或者用文字来说,人们的潜在结果Y我已经治疗或不治疗不取决于他们是否真的被(可观察的)治疗。换句话说,我们可以忽略人们是如何在一种情况下和另一种情况下结束生命的,而把他们的潜在结果看作是可以交换的。虽然这看起来很厚,但是如果我们为“理想”(潜在)世界添加“已实现”的下标和上标就变得很清楚了(由 [https://www.cambridge.org/core/books/statistical-models-and-causal-inference/7CE8D4957FF6E9615AAAC4128FA8246E David Freedman]提出的符号; 一个视觉可以在这里帮助:[https://drive.google.com/open?id=1nLHHH0il225LIy33nRiH3ZfgoX1_-_V9 potential outcomes simplified]).
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数学形式上,它被写成<math>[Y<sub>i</sub>1, Y<sub>i</sub>0] ⊥ Tx<sub>i</sub></math> ,或者用文字来说,人们的潜在结果Y我已经治疗或不治疗不取决于他们是否真的被(可观察的)治疗。换句话说,我们可以忽略人们是如何在一种情况下和另一种情况下结束生命的,而把他们的潜在结果看作是可以交换的。虽然这看起来很厚,但是如果我们为“理想”(潜在)世界添加“已实现”的下标和上标就变得很清楚了(由 [https://www.cambridge.org/core/books/statistical-models-and-causal-inference/7CE8D4957FF6E9615AAAC4128FA8246E David Freedman]提出的符号; 一个视觉可以在这里帮助:[https://drive.google.com/open?id=1nLHHH0il225LIy33nRiH3ZfgoX1_-_V9 potential outcomes simplified]).
    
So: Y<sub>1</sub><sup>1</sup>/*Y<sub>0</sub><sup>1</sup> are potential Y outcomes had the person been treated (superscript <sup>1</sup>), when in reality they have actually been (Y<sub>1</sub><sup>1</sup>, subscript <sub>1</sub>), or not (*Y<sub>0</sub><sup>1</sup>: the * signals this quantity can never be realized or observed, or is ''fully'' contrary-to-fact or counterfactual, CF).
 
So: Y<sub>1</sub><sup>1</sup>/*Y<sub>0</sub><sup>1</sup> are potential Y outcomes had the person been treated (superscript <sup>1</sup>), when in reality they have actually been (Y<sub>1</sub><sup>1</sup>, subscript <sub>1</sub>), or not (*Y<sub>0</sub><sup>1</sup>: the * signals this quantity can never be realized or observed, or is ''fully'' contrary-to-fact or counterfactual, CF).
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