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Na\"ive regression requires weaker assumptions than factor models to adjust for multiple cause confounding

arXiv.org Machine Learning

The empirical practice of using factor models to adjust for shared, unobserved confounders, $\mathbf{Z}$, in observational settings with multiple treatments, $\mathbf{A}$, is widespread in fields including genetics, networks, medicine, and politics. Wang and Blei (2019, WB) formalizes these procedures and develops the "deconfounder," a causal inference method using factor models of $\mathbf{A}$ to estimate "substitute confounders," $\hat{\mathbf{Z}}$, then estimating treatment effects by regressing the outcome, $\mathbf{Y}$, on part of $\mathbf{A}$ while adjusting for $\hat{\mathbf{Z}}$. WB claim the deconfounder is unbiased when there are no single-cause confounders and $\hat{\mathbf{Z}}$ is "pinpointed." We clarify pinpointing requires each confounder to affect infinitely many treatments. We prove under these assumptions, a na\"ive semiparametric regression of $\mathbf{Y}$ on $\mathbf{A}$ is asymptotically unbiased. Deconfounder variants nesting this regression are therefore also asymptotically unbiased, but variants using $\hat{\mathbf{Z}}$ and subsets of causes require further untestable assumptions. We replicate every deconfounder analysis with available data and find it fails to consistently outperform na\"ive regression. In practice, the deconfounder produces implausible estimates in WB's case study to movie earnings: estimates suggest comic author Stan Lee's cameo appearances causally contributed \$15.5 billion, most of Marvel movie revenue. We conclude neither approach is a viable substitute for careful research design in real-world applications.


Digital Creativity Support for Original Journalism

Communications of the ACM

Journalism involves the search for and critical analysis of information.18 How journalists discover and select sources of this information is important to avoid bias, to be credible and trusted, and to create angles with which to generate new stories of value to readers. Journalist creative thinking, to discover and generate new associations during this search and analysis of information, contributes to the generation of new stories. Journalists are known to seek opportunities to develop new creative skills with which to discover information.17 Applying these skills enables journalists to maintain control over their work.25 However, discovering and examining information sources about complex stories takes time--time that journalists increasingly lack as news organizations reduce staff numbers.22 The digitalization of news production and consumption has led many news businesses to become uncompetitive.


Digital Humans on the Big Screen

Communications of the ACM

Artificial images have been around almost as long as movies. As computing power has grown and digital photography has become commonplace, special effects have increasingly been created digitally, and have become much more realistic as a result. ACM's Turing Award for 2019 to Patrick M. Hanrahan and Edwin E. Catmull reflected in part their contributions to computer-generated imagery (CGI), notably at the pioneering animation company Pixar. CGI is best known in science fiction or other fantastic settings, where audiences presumably already have suspended their disbelief. Similarly, exotic creatures can be compelling when they display even primitive human facial expressions.



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