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Archive of posts filed under the Causal Inference category.

The Pandora Principle in statistics — and its malign converse, the ostrich

The Pandora Principle is that once you’ve considered a possible interaction or bias or confounder, you can’t un-think it. The malign converse is when people realize this and then design their studies to avoid putting themselves in a position where they have to consider some potentially important factor. For example, suppose you’re considering some policy […]

Torture talk: An uncontrolled experiment is still an experiment.

Paul Alper points us to this horrifying op-ed by M. Gregg Bloche about scientific study of data from U.S. military torture programs. I’ll leave the torture stuff to the experts or this guy who you’ve probably heard of. Instead, I have a technical point to make. In the op-ed, Bloche writes: In a true experimental […]

Does declawing cause harm?

Alex Chernavsky writes: I discovered your blog through a mutual friend – the late Seth Roberts. I’m not a statistician. I’m a cat-loving IT guy who works for an animal shelter in Upstate New York. I have a dataset that consists of 17-years’-worth of animal admissions data. When an owner surrenders an animal to us, […]

It’s hard to know what to say about an observational comparison that doesn’t control for key differences between treatment and control groups, chili pepper edition

Jonathan Falk points to this article and writes: Thoughts? I would have liked to have seen the data matched on age, rather than simply using age in a Cox regression, since I suspect that’s what really going on here. The non-chili eaters were much older, and I suspect that the failure to interact age, or […]

Multilevel modeling: What it can and cannot do

Today’s post reminded me of this article from 2005: We illustrate the strengths and limitations of multilevel modeling through an example of the prediction of home radon levels in U.S. counties. . . . Compared with the two classical estimates (no pooling and complete pooling), the inferences from the multilevel models are more reasonable. . […]

How does a Nobel-prize-winning economist become a victim of bog-standard selection bias?

Someone who wishes to remain anonymous writes in with a story: Linking to a new paper by Jorge Luis García, James J. Heckman, and Anna L. Ziff, an economist Sue Dynarski makes this “joke” on facebook—or maybe it’s not a joke: How does one adjust standard errors to account for the fact that N of […]

His concern is that the authors don’t control for the position of games within a season.

Chris Glynn wrote last year: I read your blog post about middle brow literature and PPNAS the other day. Today, a friend forwarded me this article in The Atlantic that (in my opinion) is another example of what you’ve recently been talking about. The research in question is focused on Major League Baseball and the […]

How to design future studies of systemic exercise intolerance disease (chronic fatigue syndrome)?

Someone named Ramsey writes on behalf of a self-managed support community of 100+ systemic exercise intolerance disease (SEID) patients. He read my recent article on the topic and had a question regarding the following excerpt: For conditions like S.E.I.D., then, the better approach may be to gather data from people suffering “in the wild,” combining […]

Statisticians and economists agree: We should learn from data by “generating and revising models, hypotheses, and data analyzed in response to surprising findings.” (That’s what Bayesian data analysis is all about.)

Kevin Lewis points us to this article by economist James Heckman and statistician Burton Singer, who write: All analysts approach data with preconceptions. The data never speak for themselves. Sometimes preconceptions are encoded in precise models. Sometimes they are just intuitions that analysts seek to confirm and solidify. A central question is how to revise […]

Analyze all your comparisons. That’s better than looking at the max difference and trying to do a multiple comparisons correction.

[cat picture] The following email came in: I’m in a PhD program (poli sci) with a heavy emphasis on methods. One thing that my statistics courses emphasize, but that doesn’t get much attention in my poli sci courses, is the problem of simultaneous inferences. This strikes me as a problem. I am a bit unclear […]

The Publicity Factory: How even serious research gets exaggerated by the process of scientific publication and media exposure

The starting point is that we’ve seen a lot of talk about frivolous science, headline-bait such as the study that said that married women are more likely to vote for Mitt Romney when ovulating, or the study that said that girl-named hurricanes are more deadly than boy-named hurricanes, and at this point some of these […]

The Other Side of the Night

Don Green points us to this quantitative/qualitative meta-analysis he did with Betsy Levy Paluck and Seth Green. The paper begins: This paper evaluates the state of contact hypothesis research from a policy perspective. Building on Pettigrew and Tropp’s (2006) influential meta-analysis, we assemble all intergroup contact studies that feature random assignment and delayed outcome measures, […]

Causal inference using Bayesian additive regression trees: some questions and answers

[cat picture] Rachael Meager writes: We’re working on a policy analysis project. Last year we spoke about individual treatment effects, which is the direction we want to go in. At the time you suggested BART [Bayesian additive regression trees; these are not averages of tree models as are usually set up; rather, the key is […]

Danger Sign

Melvyn Weeks writes: I [Weeks] have a question related to comparability and departures thereof in regression models. I am familiar with these issues, namely the problems of a lack of complete overlap and imbalance as applied to treatment models where there exists a binary treatment. However, it strikes me that these issues apply more generally […]

Causal inference conference in North Carolina

[cat picture] Michael Hudgens announces: Registration for the 2017 Atlantic Causal Inference Conference is now open. The registration site is here. More information about the conference, including the poster session and the Second Annual Causal Inference Data Analysis Challenge can be found on the conference website here. We held the very first Atlantic Causal Inference Conference here […]

Causal inference conference at Columbia University on Sat 6 May: Varying Treatment Effects

Hey! We’re throwing a conference: Varying Treatment Effects The literature on causal inference focuses on estimating average effects, but the very notion of an “average effect” acknowledges variation. Relevant buzzwords are treatment interactions, situational effects, and personalized medicine. In this one-day conference we shall focus on varying effects in social science and policy research, with […]

Let’s accept the idea that treatment effects vary—not as something special but just as a matter of course

Tyler Cowen writes: Does knowing the price lower your enjoyment of goods and services? I [Cowen] don’t quite agree with this as stated, as the experience of enjoying a bargain can make it more pleasurable, or at least I have seen this for many people. Some in fact enjoy the bargain only, not the actual […]

This could be a big deal: the overuse of psychotropic medications for advanced Alzheimer’s patients

I received the following email, entitled “A research lead (potentially bigger than the opioid epidemic,” from someone who wishes to remain anonymous: My research lead is related to the use of psychotropic medications in Alzheimer’s patients. I should note that strong cautions have already been issued with respect to the use of these medications in […]

Applying statistics in science will likely remain unreasonably difficult in my life time: but I have no intention of changing careers.

This post is by Keith. image   (Image from deviantart.com) There are a couple posts I have been struggling to put together, one is on what science is or should be (drawing on Charles Peirce). The other is on why a posterior is not a posterior is not a posterior: even if mathematically equivalent – they […]

How to do a descriptive analysis using regression modeling?

Freddy Garcia writes: I read your post Vine regression?, and your phrase “I love descriptive data analysis!” make me wonder: How to do a descriptive analysis using regression models? Maybe my question could be misleading to an statistician, but I am a economics student. So we are accustomed to think in causal terms when we […]