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arXiv 1801.06282stat.ME
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空间相关多元时间序列因果推断的贝叶斯方法

Bayesian method for causal inference in spatially-correlated multivariate time series

Bo Ning, Subhashis Ghosal, Jewell Thomas

摘要:

衡量广告活动对销售的因果影响是广告公司的一项重要任务。当公司在空间相关的多个商店中进行广告活动时,以及当销售数据具有低信噪比使得广告效果难以检测时,挑战就会出现。本文提出了解决这两个挑战的解决方案。提出了一种新的贝叶斯方法来检测较弱的影响和多变量结构时间序列模型被用来捕捉商店之间的空间相关性,通过放置一个$\mathcal{G}$ -Wishart先验的精度矩阵。新方法是比较一个潜变量的两个后验分布--一个是由测试商店的观测数据得到的,另一个是由它们的反事实潜在结果的数据得到的。反事实的潜在结果是从综合控制的数据中估计出来的,每个数据都是因果期间许多控制商店的销售数字的线性组合。控制悬挂物的选择采用修正的期望最大化变量选择(EMVS)方法。提出了一种两阶段算法来估计模型的参数。为了防止预测区间爆炸,通过最近提出的先验知识对模型的局部线性趋势施加平稳性约束。本文讨论了使用此先验的好处。详细的仿真研究表明,使用我们提出的方法来检测较弱的因果影响的有效性。新方法被应用于衡量的因果关系的影响,在一个大型的全国性零售连锁店的商店销售的消费品的广告活动。

英文摘要:

Measuring the causal impact of an advertising campaign on sales is an essential task for advertising companies. Challenges arise when companies run advertising campaigns in multiple stores which are spatially correlated, and when the sales data have a low signal-to-noise ratio which makes the advertising effects hard to detect. This paper proposes a solution to address both of these challenges. A novel Bayesian method is proposed to detect weaker impacts and a multivariate structural time series model is used to capture the spatial correlation between stores through placing a $\mathcal{G}$-Wishart prior on the precision matrix. The new method is to compare two posterior distributions of a latent variable---one obtained by using the observed data from the test stores and the other one obtained by using the data from their counterfactual potential outcomes. The counterfactual potential outcomes are estimated from the data of synthetic controls, each of which is a linear combination of sales figures at many control stores over the causal period. Control stores are selected using a revised Expectation-Maximization variable selection (EMVS) method. A two-stage algorithm is proposed to estimate the parameters of the model. To prevent the prediction intervals from being explosive, a stationarity constraint is imposed on the local linear trend of the model through a recently proposed prior. The benefit of using this prior is discussed in this paper. A detailed simulation study shows the effectiveness of using our proposed method to detect weaker causal impact. The new method is applied to measure the causal effect of an advertising campaign for a consumer product sold at stores of a large national retail chain.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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