Our aging population increasingly suffers from multiple chronic diseases simultaneously, necessitating the comprehensive treatment of these conditions. Finding the optimal set of drugs for a combinatorial set of diseases is a combinatorial pattern exploration problem. Association rule mining is a popular tool for such problems, but the requirement of health care for finding causal, rather than associative, patterns renders association rule mining unsuitable. To address this issue, we propose a novel framework based on the Rubin-Neyman causal model for extracting causal rules from observational data, correcting for a number of common biases. Specifically, given a set of interventions and a set of items that define subpopulations (e.g., diseases), we wish to find all subpopulations in which effective intervention combinations exist and in each such subpopulation, we wish to find all intervention combinations such that dropping any intervention from this combination will reduce the efficacy of the treatment. A key aspect of our framework is the concept of closed intervention sets which extend the concept of quantifying the effect of a single intervention to a set of concurrent interventions. We also evaluated our causal rule mining framework on the Electronic Health Records (EHR) data of a large cohort of patients from Mayo Clinic and showed that the patterns we extracted are sufficiently rich to explain the controversial findings in the medical literature regarding the effect of a class of cholesterol drugs on Type-II Diabetes Mellitus (T2DM).
Online search systems that display ads continually offer new features that advertisers can use to fine-tune and enhance their ad campaigns. An important question is whether a new feature actually helps advertisers. In an ideal world for statisticians, we would answer this question by running a statistically designed experiment. But that would require randomly choosing a set of advertisers and forcing them to use the feature, which is not realistic. Accordingly, in the real world, new features for advertisers are seldom evaluated with a traditional experimental protocol. Instead, customer service representatives select advertisers who are invited to be among the first to test a new feature (i.e., white-listed), and then each white-listed advertiser chooses whether or not to use the new feature. Neither the customer service representative nor the advertiser chooses at random. This paper addresses the problem of drawing valid inferences from whitelist trials about the effects of new features on advertiser happiness. We are guided by three principles. First, statistical procedures for whitelist trials are likely to be applied in an automated way, so they should be robust to violations of modeling assumptions. Second, standard analysis tools should be preferred over custom-built ones, both for clarity and for robustness. Standard tools have withstood the test of time and have been thoroughly debugged. Finally, it should be easy to compute reliable confidence intervals for the estimator. We review an estimator that has all these attributes, allowing us to make valid inferences about the effects of a new feature on advertiser happiness. Display ads proliferate on the web, but are they effective? Or are they irrelevant in light of all the other advertising that people see? We describe a way to answer these questions, quickly and accurately, without randomized experiments, surveys, focus groups or expert data analysts. Doubly robust estimation protects against the selection bias that is inherent in observational data, and a nonparametric test that is based on irrelevant outcomes provides further defense. Simulations based on realistic scenarios show that the resulting estimates are more robust to selection bias than traditional alternatives, such as regression modeling or propensity scoring. Moreover, computations are fast enough that all processing, from data retrieval through estimation, testing, validation and report generation, proceeds in an automated pipeline, without anyone needing to see the raw data.