本文提出了一种估计溢出效应存在福利最大化政策的实验设计。我考虑一个设置在其中组织成一个有限数量的大型群集,并在每个群集中以不观察到的方式交互。作为第一种贡献,我介绍了一个单波实验,以估计治疗概率的变化的边际效应,以考虑到溢出率,并测试政策最优性。该设计在群集中独立地随机化处理,并诱导局部扰动到对簇成对的治疗概率。使用估计的边际效应,我构建了对定期治疗分配规则最大化福利的实际测试,并且我表征了其渐近性质。该想法是,研究人员应报告对福利最大化政策的边际效应和测试的估计:边际效应表明福利改善的方向,并提供了关于是否值得进行额外实验以估计估计福利改善的证据治疗分配。作为第二种贡献,我设计了多波实验来估计治疗分配规则并最大化福利。我获得了小型样本保证,最大可获得的福利和估计政策(遗憾)评估的福利之间的差异。这种保证的必要性是,遗憾在迭代和集群的数量中线性会聚到零。校准在信息扩散和现金转移方案上校准的模拟表明,该方法导致了显着的福利改进。
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针对社会福利计划中个人的干预措施的主要问题之一是歧视:个性化治疗可能导致跨年龄,性别或种族等敏感属性的差异。本文解决了公平有效的治疗分配规则的设计问题。我们采用了第一次的非遗憾视角,没有危害:我们选择了帕累托边境中最公平的分配。我们将优化投入到混合构成线性程序公式中,可以使用现成的算法来解决。我们对估计的政策功能的不公平性和在帕累托前沿的不公平保证在一般公平概念下的不公平性范围内得出了遗憾。最后,我们使用教育经济学的应用来说明我们的方法。
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了解特定待遇或政策与许多感兴趣领域有关的影响,从政治经济学,营销到医疗保健。在本文中,我们开发了一种非参数算法,用于在合成控制的背景下检测随着时间的流逝的治疗作用。该方法基于许多算法的反事实预测,而不必假设该算法正确捕获模型。我们介绍了一种推论程序来检测治疗效果,并表明测试程序对于固定,β混合过程渐近有效,而无需对所考虑的一组基础算法施加任何限制。我们讨论了平均治疗效果估计的一致性保证,并为提出的方法提供了遗憾的界限。算法类别可能包括随机森林,套索或任何其他机器学习估计器。数值研究和应用说明了该方法的优势。
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Decision makers often aim to learn a treatment assignment policy under a capacity constraint on the number of agents that they can treat. When agents can respond strategically to such policies, competition arises, complicating the estimation of the effect of the policy. In this paper, we study capacity-constrained treatment assignment in the presence of such interference. We consider a dynamic model where the decision maker allocates treatments at each time step and heterogeneous agents myopically best respond to the previous treatment assignment policy. When the number of agents is large but finite, we show that the threshold for receiving treatment under a given policy converges to the policy's mean-field equilibrium threshold. Based on this result, we develop a consistent estimator for the policy effect. In simulations and a semi-synthetic experiment with data from the National Education Longitudinal Study of 1988, we demonstrate that this estimator can be used for learning capacity-constrained policies in the presence of strategic behavior.
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在本文中,我们研究了在一组单位上进行的设计实验的问题,例如在线市场中的用户或用户组,以多个时间段,例如数周或数月。这些实验特别有助于研究对当前和未来结果具有因果影响的治疗(瞬时和滞后的影响)。设计问题涉及在实验之前或期间选择每个单元的治疗时间,以便最精确地估计瞬间和滞后的效果,实验后。这种治疗决策的优化可以通过降低其样本尺寸要求,直接最小化实验的机会成本。优化是我们提供近最优解的NP-Hard整数程序,当时在开始时进行设计决策(固定样本大小设计)。接下来,我们研究允许在实验期间进行适应性决策的顺序实验,并且还可能早期停止实验,进一步降低其成本。然而,这些实验的顺序性质使设计阶段和估计阶段复杂化。我们提出了一种新的算法,PGAE,通过自适应地制造治疗决策,估算治疗效果和绘制有效的实验后推理来解决这些挑战。 PGAE将来自贝叶斯统计,动态编程和样品分裂的思想结合起来。使用来自多个域的真实数据集的合成实验,我们证明了与基准相比,我们的固定样本尺寸和顺序实验的提出解决方案将实验的机会成本降低了50%和70%。
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我们探索了一个新的强盗实验模型,其中潜在的非组织序列会影响武器的性能。上下文 - 统一算法可能会混淆,而那些执行正确的推理面部信息延迟的算法。我们的主要见解是,我们称之为Deconfounst Thompson采样的算法在适应性和健壮性之间取得了微妙的平衡。它的适应性在易于固定实例中带来了最佳效率,但是在硬性非平稳性方面显示出令人惊讶的弹性,这会导致其他自适应算法失败。
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套索是一种高维回归的方法,当时,当协变量$ p $的订单数量或大于观测值$ n $时,通常使用它。由于两个基本原因,经典的渐近态性理论不适用于该模型:$(1)$正规风险是非平滑的; $(2)$估算器$ \ wideHat {\ boldsymbol {\ theta}} $与true参数vector $ \ boldsymbol {\ theta}^*$无法忽略。结果,标准的扰动论点是渐近正态性的传统基础。另一方面,套索估计器可以精确地以$ n $和$ p $大,$ n/p $的订单为一。这种表征首先是在使用I.I.D的高斯设计的情况下获得的。协变量:在这里,我们将其推广到具有非偏差协方差结构的高斯相关设计。这是根据更简单的``固定设计''模型表示的。我们在两个模型中各种数量的分布之间的距离上建立了非反应界限,它们在合适的稀疏类别中均匀地固定在信号上$ \ boldsymbol {\ theta}^*$。作为应用程序,我们研究了借助拉索的分布,并表明需要校正程度对于计算有效的置信区间是必要的。
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由于在数据稀缺的设置中,交叉验证的性能不佳,我们提出了一个新颖的估计器,以估计数据驱动的优化策略的样本外部性能。我们的方法利用优化问题的灵敏度分析来估计梯度关于数据中噪声量的最佳客观值,并利用估计的梯度将策略的样本中的表现为依据。与交叉验证技术不同,我们的方法避免了为测试集牺牲数据,在训练和因此非常适合数据稀缺的设置时使用所有数据。我们证明了我们估计量的偏见和方差范围,这些问题与不确定的线性目标优化问题,但已知的,可能是非凸的,可行的区域。对于更专业的优化问题,从某种意义上说,可行区域“弱耦合”,我们证明结果更强。具体而言,我们在估算器的错误上提供明确的高概率界限,该估计器在策略类别上均匀地保持,并取决于问题的维度和策略类的复杂性。我们的边界表明,在轻度条件下,随着优化问题的尺寸的增长,我们的估计器的误差也会消失,即使可用数据的量仍然很小且恒定。说不同的是,我们证明我们的估计量在小型数据中的大规模政权中表现良好。最后,我们通过数值将我们提出的方法与最先进的方法进行比较,通过使用真实数据调度紧急医疗响应服务的案例研究。我们的方法提供了更准确的样本外部性能估计,并学习了表现更好的政策。
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当结果取决于代理在社会或经济网络中如何联系时,我们提出了一个新的非参数建模框架。这种网络干扰描述了治疗溢出,社会互动,社会学习,信息扩散,疾病和金融蔓延,社会资本形成等大的文献。我们的方法通过首先表征在网络中使用其他代理和附近的连接在网络中链接到网络中的方法,如路径距离所测量的连接。然后通过汇集相似配置的代理的结果数据来学习策略或治疗分配的影响。我们通过提出对政策不相关/无治疗效果的假设的渐近有效测试来展示方法,并限制K-Collect-Exbeld估计器的平均平均误差,以实现平均或分布策略效应/治疗响应。
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We consider after-study statistical inference for sequentially designed experiments wherein multiple units are assigned treatments for multiple time points using treatment policies that adapt over time. Our goal is to provide inference guarantees for the counterfactual mean at the smallest possible scale -- mean outcome under different treatments for each unit and each time -- with minimal assumptions on the adaptive treatment policy. Without any structural assumptions on the counterfactual means, this challenging task is infeasible due to more unknowns than observed data points. To make progress, we introduce a latent factor model over the counterfactual means that serves as a non-parametric generalization of the non-linear mixed effects model and the bilinear latent factor model considered in prior works. For estimation, we use a non-parametric method, namely a variant of nearest neighbors, and establish a non-asymptotic high probability error bound for the counterfactual mean for each unit and each time. Under regularity conditions, this bound leads to asymptotically valid confidence intervals for the counterfactual mean as the number of units and time points grows to $\infty$.
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Estimating causal effects has become an integral part of most applied fields. Solving these modern causal questions requires tackling violations of many classical causal assumptions. In this work we consider the violation of the classical no-interference assumption, meaning that the treatment of one individuals might affect the outcomes of another. To make interference tractable, we consider a known network that describes how interference may travel. However, unlike previous work in this area, the radius (and intensity) of the interference experienced by a unit is unknown and can depend on different sub-networks of those treated and untreated that are connected to this unit. We study estimators for the average direct treatment effect on the treated in such a setting. The proposed estimator builds upon a Lepski-like procedure that searches over the possible relevant radii and treatment assignment patterns. In contrast to previous work, the proposed procedure aims to approximate the relevant network interference patterns. We establish oracle inequalities and corresponding adaptive rates for the estimation of the interference function. We leverage such estimates to propose and analyze two estimators for the average direct treatment effect on the treated. We address several challenges steaming from the data-driven creation of the patterns (i.e. feature engineering) and the network dependence. In addition to rates of convergence, under mild regularity conditions, we show that one of the proposed estimators is asymptotically normal and unbiased.
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Classical asymptotic theory for statistical inference usually involves calibrating a statistic by fixing the dimension $d$ while letting the sample size $n$ increase to infinity. Recently, much effort has been dedicated towards understanding how these methods behave in high-dimensional settings, where $d$ and $n$ both increase to infinity together. This often leads to different inference procedures, depending on the assumptions about the dimensionality, leaving the practitioner in a bind: given a dataset with 100 samples in 20 dimensions, should they calibrate by assuming $n \gg d$, or $d/n \approx 0.2$? This paper considers the goal of dimension-agnostic inference; developing methods whose validity does not depend on any assumption on $d$ versus $n$. We introduce an approach that uses variational representations of existing test statistics along with sample splitting and self-normalization to produce a new test statistic with a Gaussian limiting distribution, regardless of how $d$ scales with $n$. The resulting statistic can be viewed as a careful modification of degenerate U-statistics, dropping diagonal blocks and retaining off-diagonal blocks. We exemplify our technique for some classical problems including one-sample mean and covariance testing, and show that our tests have minimax rate-optimal power against appropriate local alternatives. In most settings, our cross U-statistic matches the high-dimensional power of the corresponding (degenerate) U-statistic up to a $\sqrt{2}$ factor.
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This paper provides estimation and inference methods for a conditional average treatment effects (CATE) characterized by a high-dimensional parameter in both homogeneous cross-sectional and unit-heterogeneous dynamic panel data settings. In our leading example, we model CATE by interacting the base treatment variable with explanatory variables. The first step of our procedure is orthogonalization, where we partial out the controls and unit effects from the outcome and the base treatment and take the cross-fitted residuals. This step uses a novel generic cross-fitting method we design for weakly dependent time series and panel data. This method "leaves out the neighbors" when fitting nuisance components, and we theoretically power it by using Strassen's coupling. As a result, we can rely on any modern machine learning method in the first step, provided it learns the residuals well enough. Second, we construct an orthogonal (or residual) learner of CATE -- the Lasso CATE -- that regresses the outcome residual on the vector of interactions of the residualized treatment with explanatory variables. If the complexity of CATE function is simpler than that of the first-stage regression, the orthogonal learner converges faster than the single-stage regression-based learner. Third, we perform simultaneous inference on parameters of the CATE function using debiasing. We also can use ordinary least squares in the last two steps when CATE is low-dimensional. In heterogeneous panel data settings, we model the unobserved unit heterogeneity as a weakly sparse deviation from Mundlak (1978)'s model of correlated unit effects as a linear function of time-invariant covariates and make use of L1-penalization to estimate these models. We demonstrate our methods by estimating price elasticities of groceries based on scanner data. We note that our results are new even for the cross-sectional (i.i.d) case.
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在因果推理和强盗文献中,基于观察数据的线性功能估算线性功能的问题是规范的。我们分析了首先估计治疗效果函数的广泛的两阶段程序,然后使用该数量来估计线性功能。我们证明了此类过程的均方误差上的非反应性上限:这些边界表明,为了获得非反应性最佳程序,应在特定加权$ l^2 $中最大程度地估算治疗效果的误差。 -规范。我们根据该加权规范的约束回归分析了两阶段的程序,并通过匹配非轴突局部局部最小值下限,在有限样品中建立了实例依赖性最优性。这些结果表明,除了取决于渐近效率方差之外,最佳的非质子风险除了取决于样本量支持的最富有函数类别的真实结果函数与其近似类别之间的加权规范距离。
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在当今的社会中,算法建议和决策已经变得普遍存在。其中许多和其他数据驱动的政策,特别是在公共政策领域,基于已知的确定性规则,以确保其透明度和可解释性。例如,算法预审风险评估,即作为我们的激励申请,提供相对简单,确定性的分类分数和建议,以帮助法官发出释放决策。我们如何根据现有的确定性政策使用数据,并学习新的和更好的策略?不幸的是,策略学习的先前方法不适用,因为它们需要现有的政策是随机而非确定性的。我们开发了一种强大的优化方法,部分地识别策略的预期效用,然后通过最小化最坏情况后悔找到最佳策略。由此产生的政策是保守的,但具有统计安全保障,允许政策制定者限制产生比现有政策更糟糕的结果的可能性。我们将这种方法扩展到人类借助算法建议作出决策的共同和重要的环境。最后,我们将提议的方法应用于预审风险评估工具的独特现场实验。我们推出了新的分类和推荐规则,以保留现有仪器的透明度和可解释性,同时可能以较低的成本导致更好的整体结果。
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预测一组结果 - 而不是独特的结果 - 是统计学习中不确定性定量的有前途的解决方案。尽管有关于构建具有统计保证的预测集的丰富文献,但适应未知的协变量转变(实践中普遍存在的问题)还是一个严重的未解决的挑战。在本文中,我们表明具有有限样本覆盖范围保证的预测集是非信息性的,并提出了一种新型的无灵活分配方法PredSet-1Step,以有效地构建了在未知协方差转移下具有渐近覆盖范围保证的预测集。我们正式表明我们的方法是\ textIt {渐近上可能是近似正确},对大型样本的置信度有很好的覆盖误差。我们说明,在南非队列研究中,它在许多实验和有关HIV风险预测的数据集中实现了名义覆盖范围。我们的理论取决于基于一般渐近线性估计器的WALD置信区间覆盖范围的融合率的新结合。
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A / B测试或在线实验是一种标准的业务策略,可以在制药,技术和传统行业中与旧产品进行比较。在双面市场平台(例如优步)的在线实验中出现了主要挑战,其中只有一个单位接受一系列处理随着时间的推移。在这些实验中,给定时间的治疗会影响当前结果以及未来的结果。本文的目的是引入用于在这些实验中携带A / B测试的加强学习框架,同时表征长期治疗效果。我们所提出的测试程序允许顺序监控和在线更新。它通常适用于不同行业的各种治疗设计。此外,我们系统地研究了我们测试程序的理论特性(例如,尺寸和功率)。最后,我们将框架应用于模拟数据和从技术公司获得的真实数据示例,以说明其在目前的实践中的优势。我们的测试的Python实现是在https://github.com/callmespring/causalrl上找到的。
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在本文中,我们提出了一种非参数估计的方法,并推断了一般样本选择模型中因果效应参数的异质界限,初始治疗可能会影响干预后结果是否观察到。可观察到的协变量可能会混淆治疗选择,而观察结果和不可观察的结果可能会混淆。该方法提供条件效应界限作为策略相关的预处理变量的功能。它允许对身份不明的条件效应曲线进行有效的统计推断。我们使用灵活的半参数脱偏机学习方法,该方法可以适应柔性功能形式和治疗,选择和结果过程之间的高维混杂变量。还提供了易于验证的高级条件,以进行估计和错误指定的鲁棒推理保证。
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算法在政策和业务中产生越来越多的决策和建议。这种算法决策是自然实验(可条件准随机分配的仪器),因为该算法仅基于可观察输入变量的决定。我们使用该观察来为一类随机和确定性决策算法开发治疗效果估算器。我们的估算器被证明对于明确的因果效应,它们是一致的和渐近正常的。我们估算器的一个关键特例是多维回归不连续性设计。我们应用估算员以评估冠状病毒援助,救济和经济安全(关心)法案的效果,其中数十亿美元的资金通过算法规则分配给医院。我们的估计表明,救济资金对Covid-19相关的医院活动水平影响不大。天真的OLS和IV估计表现出实质性的选择偏差。
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In the classical setting of self-selection, the goal is to learn $k$ models, simultaneously from observations $(x^{(i)}, y^{(i)})$ where $y^{(i)}$ is the output of one of $k$ underlying models on input $x^{(i)}$. In contrast to mixture models, where we observe the output of a randomly selected model, here the observed model depends on the outputs themselves, and is determined by some known selection criterion. For example, we might observe the highest output, the smallest output, or the median output of the $k$ models. In known-index self-selection, the identity of the observed model output is observable; in unknown-index self-selection, it is not. Self-selection has a long history in Econometrics and applications in various theoretical and applied fields, including treatment effect estimation, imitation learning, learning from strategically reported data, and learning from markets at disequilibrium. In this work, we present the first computationally and statistically efficient estimation algorithms for the most standard setting of this problem where the models are linear. In the known-index case, we require poly$(1/\varepsilon, k, d)$ sample and time complexity to estimate all model parameters to accuracy $\varepsilon$ in $d$ dimensions, and can accommodate quite general selection criteria. In the more challenging unknown-index case, even the identifiability of the linear models (from infinitely many samples) was not known. We show three results in this case for the commonly studied $\max$ self-selection criterion: (1) we show that the linear models are indeed identifiable, (2) for general $k$ we provide an algorithm with poly$(d) \exp(\text{poly}(k))$ sample and time complexity to estimate the regression parameters up to error $1/\text{poly}(k)$, and (3) for $k = 2$ we provide an algorithm for any error $\varepsilon$ and poly$(d, 1/\varepsilon)$ sample and time complexity.
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