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Archive of posts filed under the Multilevel Modeling category.

UK election summary

The Conservative party, led by Theresa May, defeated the Labour party, led by Jeremy Corbyn. The Conservative party got 42% of the vote, Labour got 40% of the vote, and all the other parties received 18% between them. The Conservatives ended up with 51.5% of the two-party vote, just a bit less than Hillary Clinton’s […]

No conf intervals? No problem (if you got replication).

This came up in a research discussion the other day. Someone had produced some estimates, and there was a question: where are the conf intervals. I said that if you have replication and you graph the estimates that were produced, then you don’t really need conf intervals (or, for that matter, p-values). The idea is […]

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 […]

U.K. news article congratulates YouGov on using modern methods in polling inference

Mike Betancourt pointed me to this news article by Alan Travis that is refreshingly positive regarding the use of sophisticated statistical methods in analyzing opinion polls. Here’s Travis: Leading pollsters have described YouGov’s “shock poll” predicting a hung parliament on 8 June as “brave” and the decision by the Times to splash it on its […]

Come to Seattle to work with us on Stan!

Our colleague Jon Wakefield in the Department of Biostatistics at the University of Washington is interested in supervising a 2-year postdoc through this training program. We’re interested in finding someone who would with Jon and another faculty member (who is assigned on the basis of interests) on exciting projects in spatio-temporal modeling and the environmental […]

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, […]


I think there’s something wrong this op-ed by developmental psychologist Alison Gopnik, “4-year-olds don’t act like Trump,” and which begins, The analogy is pervasive among his critics: Donald Trump is like a child. . . . But the analogy is profoundly wrong, and it’s unfair to children. The scientific developmental research of the past 30 […]

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 […]

Using Stan for week-by-week updating of estimated soccer team abilites

Milad Kharratzadeh shares this analysis of the English Premier League during last year’s famous season. He fit a Bayesian model using Stan, and the R markdown file is here. The analysis has three interesting features: 1. Team ability is allowed to continuously vary throughout the season; thus, once the season is over, you can see […]

Splines in Stan! (including priors that enforce smoothness)

Milad Kharratzadeh shares a new case study. This could be useful to a lot of people. And here’s the markdown file with every last bit of R and Stan code. Just for example, here’s the last section of the document, which shows how to simulate the data and fit the model graphed above: Location of […]

A completely reasonable-sounding statement with which I strongly disagree

From a couple years ago: In the context of a listserv discussion about replication in psychology experiments, someone wrote: The current best estimate of the effect size is somewhere in between the original study and the replication’s reported value. This conciliatory, split-the-difference statement sounds reasonable, and it might well represent good politics in the context […]

The Bolt from the Blue

Lionel Hertzog writes: In the method section of a recent Nature article in my field of research (diversity-ecosystem function) one can read the following: The inclusion of many predictors in statistical models increases the chance of type I error (false positives). To account for this we used a Bernoulli process to detect false discovery rates, […]

Update rstanarm to version 2.15.3

Ben Goodrich writes: We just released rstanarm 2.15.3, which fixed a major bug that was introduced back in January with the 2.14.1 release where models of the form stan_glmer(y ~ … + (1 | group1) + (1 | group2), family = binomial()) would produce WRONG RESULTS. This only applies to Bernoulli models with multiple group-specific […]

The next Lancet retraction? [“Subcortical brain volume differences in participants with attention deficit hyperactivity disorder in children and adults”]

[cat picture] Someone who prefers to remain anonymous asks for my thoughts on this post by Michael Corrigan and Robert Whitaker, “Lancet Psychiatry Needs to Retract the ADHD-Enigma Study: Authors’ conclusion that individuals with ADHD have smaller brains is belied by their own data,” which begins: Lancet Psychiatry, a UK-based medical journal, recently published a […]

Prediction model for fleet management

Chang writes: I am working on a fleet management system these days: basically, I am trying to predict the usage ‘y’ of our fleet in a zip code in the future. We have some factors ‘X’, such as number of active users, number of active merchants etc. If I can fix the time horizon, the […]

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 […]

Mortality rate trends by age, ethnicity, sex, and state (link fixed)

There continues to be a lot of discussion on the purported increase in mortality rates among middle-aged white people in America. Actually an increase among women and not much change among men but you don’t hear so much about this as it contradicts the “struggling white men” story that we hear so much about in […]

Whassup, Pace investigators? You’re still hiding your data. C’mon dudes, loosen up. We’re getting chronic fatigue waiting for you already!

[cat picture] James Coyne writes: For those of you who have not heard of the struggle for release of the data from the publicly funded PACE trial of adaptive pacing therapy, cognitive behaviour therapy, graded exercise therapy, and specialist medical care for chronic fatigue syndrome, you can access my [Coyne’s] initial call for release of […]

“Bias” and “variance” are two ways of looking at the same thing. (“Bias” is conditional, “variance” is unconditional.)

Someone asked me about the distinction between bias and noise and I sent him some links. Then I thought this might interest some of you too, so here it is: Here’s a recent paper on election polling where we try to be explicit about what is bias and what is variance: And here are some […]

“A blog post that can help an industry”

Tim Bock writes: I understood how to address weights in statistical tests by reading Lu and Gelman (2003). Thanks. You may be disappointed to know that this knowledge allowed me to write software, which has been used to compute many billions of p-values. When I read your posts and papers on forking paths, I always […]