My enemies are all too familiar. They’re the ones who used to call me friend – Jawbreaker Well I am back from Australia where I gave a whole pile of talks and drank more coffee than is probably a good idea. So I’m pretty jetlagged and I’m supposed to be writing my tenure packet, so […]

**Multilevel Modeling**category.

## What can be learned from this study?

James Coyne writes: A recent article co-authored by a leading mindfulness researcher claims to address the problems that plague meditation research, namely, underpowered studies; lack of or meaningful control groups; and an exclusive reliance on subjective self-report measures, rather than measures of the biological substrate that could establish possible mechanisms. The article claims adequate sample […]

## As always, I think the best solution is not for researchers to just report on some preregistered claim, but rather for them to display the entire multiverse of possible relevant results.

I happened to receive these two emails in the same day. Russ Lyons pointed to this news article by Jocelyn Kaiser, “Major medical journals don’t follow their own rules for reporting results from clinical trials,” and Kevin Lewis pointed to this research article by Kevin Murphy and Herman Aguinis, “HARKing: How Badly Can Cherry-Picking and […]

## “Beyond ‘Treatment Versus Control’: How Bayesian Analysis Makes Factorial Experiments Feasible in Education Research”

Daniel Kassler, Ira Nichols-Barrer, and Mariel Finucane write: Researchers often wish to test a large set of related interventions or approaches to implementation. A factorial experiment accomplishes this by examining not only basic treatment–control comparisons but also the effects of multiple implementation “factors” such as different dosages or implementation strategies and the interactions between these […]

## Multilevel Bayesian analyses of the growth mindset experiment

Jared Murray, one of the coauthors of the Growth Mindset study we discussed yesterday, writes: Here are some pointers to details about the multilevel Bayesian modeling we did in the Nature paper, and some notes about ongoing & future work. We did a Bayesian analysis not dissimilar to the one you wished for! In section […]

## “Study finds ‘Growth Mindset’ intervention taking less than an hour raises grades for ninth graders”

I received this press release in the mail: Study finds ‘Growth Mindset’ intervention taking less than an hour raises grades for ninth graders Intervention is first to show national applicability, breaks new methodological ground – Study finds low-cost, online growth mindset program taking less than an hour can improve ninth graders’ academic achievement – The […]

## Allowing intercepts and slopes to vary in a logistic regression: how does this change the ROC curve?

Jonathan Hughes writes: I am an engineering doctoral student. As part of my dissertation I’m proposing a mode of adaptation for a predictive system to individual subgroup specific streams of data which come each from a specific subgroup of a mixture population distribution. As part of the proposal presentation someone referenced your work and believed […]

## The garden of forking paths

Bert Gunter points us to this editorial: So, researchers using these data to answer questions about the effects of technology [screen time on adolescents] need to make several decisions. Depending on the complexity of the data set, variables can be statistically analysed in trillions of ways. This makes almost any pattern of results possible. As […]

## I don’t have a clever title but this is an interesting paper

Why do we, as a discipline, have so little understanding of the methods we have created and promote? Our primary tool for gaining understanding is mathematics, which has obvious appeal: most of us trained in math and there is no better form of information than a theorem that establishes a useful fact about a method. […]

## The Economist does Mister P

Elliott Morris points us to this magazine article, “If everyone had voted, Hillary Clinton would probably be president,” which reports: Close observers of America know that the rules of its democracy often favour Republicans. But the party’s biggest advantage may be one that is rarely discussed: turnout is just 60%, low for a rich country. […]

## Causal inference with time-varying mediators

Adan Becerra writes to Tyler VanderWeele: I have a question about your paper “Mediation analysis for a survival outcome with time-varying exposures, mediators, and confounders” that I was hoping that you could help my colleague (Julia Ward) and me with. We are currently using Medicare claims data to evaluate the following general mediation among dialysis […]

## The garden of 603,979,752 forking paths

Amy Orben and Andrew Przybylski write: The widespread use of digital technologies by young people has spurred speculation that their regular use negatively impacts psychological well-being. Current empirical evidence supporting this idea is largely based on secondary analyses of large-scale social datasets. Though these datasets provide a valuable resource for highly powered investigations, their many […]

## Random patterns in data yield random conclusions.

Bert Gunter points to this New York Times article, “How Exercise May Make Us Healthier: People who exercise have different proteins moving through their bloodstreams than those who are generally sedentary,” writing that it is “hyping a Journal of Applied Physiology paper that is now my personal record holder for most extensive conclusions from practically […]

## We’re done with our Applied Regression final exam (and solution to question 15)

We’re done with our exam. And the solution to question 15: 15. Consider the following procedure. • Set n = 100 and draw n continuous values x_i uniformly distributed between 0 and 10. Then simulate data from the model y_i = a + bx_i + error_i, for i = 1,…,n, with a = 2, b […]

## Pharmacometrics meeting in Paris on the afternoon of 11 July 2019

Julie Bertrand writes: The pharmacometrics group led by France Mentre (IAME, INSERM, Univ Paris) is very pleased to host a free ISoP Statistics and Pharmacometrics (SxP) SIG local event at Faculté Bichat, 16 rue Henri Huchard, 75018 Paris, on Thursday afternoon the 11th of July 2019. It will features talks from Professor Andrew Gelman, Univ […]

## Question 15 of our Applied Regression final exam (and solution to question 14)

Here’s question 15 of our exam: 15. Consider the following procedure. • Set n = 100 and draw n continuous values x_i uniformly distributed between 0 and 10. Then simulate data from the model y_i = a + bx_i + error_i, for i = 1,…,n, with a = 2, b = 3, and independent errors […]

## Question 14 of our Applied Regression final exam (and solution to question 13)

Here’s question 14 of our exam: 14. You are predicting whether a student passes a class given pre-test score. The fitted model is, Pr(Pass) = logit^−1(a_j + 0.1x), for a student in classroom j whose pre-test score is x. The pre-test scores range from 0 to 50. The a_j’s are estimated to have a normal […]

## Question 13 of our Applied Regression final exam (and solution to question 12)

Here’s question 13 of our exam: 13. You fit a model of the form: y ∼ x + u full + (1 | group). The estimated coefficients are 2.5, 0.7, and 0.5 respectively for the intercept, x, and u full, with group and individual residual standard deviations estimated as 2.0 and 3.0 respectively. Write the […]

## Question 7 of our Applied Regression final exam (and solution to question 6)

Here’s question 7 of our exam: 7. You conduct an experiment in which some people get a special get-out-the-vote message and others do not. Then you follow up with a sample, after the election, to see if they voted. If you follow up with 500 people, how large an effect would you be able to […]

## My talks at the University of Chicago this Thursday and Friday

Political Economy Workshop (12:30pm, Thurs 23 May 2019, Room 1022 of Harris Public Policy (Keller Center) 1307 E 60th Street): Political Science and the Replication Crisis We’ve heard a lot about the replication crisis in science (silly studies about ESP, evolutionary psychology, miraculous life hacks, etc.), how it happened (p-values, forking paths), and proposed remedies […]