Articles by Kristoffer Magnusson

Heterogeneous treatment effects and homogeneous outcome variances

January 10, 2020 | 0 Comments

Recently there has been a couple of meta-analyses investigating heterogeneous treatment effects by analyzing the ratio of the outcome variances in the treatment and control group. The argument made in these articles is that if individuals differ in their response, then observed variances in the treatment and control group in ...
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Mediation, confounding, and measurement error

October 9, 2019 | 0 Comments

Mediation might be the ultimate example of how a method continues to be used despite a vast number of papers and textbooks describing the extremely strong assumptions required to estimate unbiased effects. My aim with this post is not to show some fancy method that could help reduce bias; rather ...
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Change over time is not “treatment response”

November 19, 2018 | 0 Comments

This will be a non-technical post illustrating the problems with identifying treatment responders or non-responders using inappropriate within-group analyses. Specifically, I will show why it is pointless to try to identify a subgroup of non-responders using a naïve analysis of data from one treatment group only, even though we ...
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Do you really need a multilevel model? A preview of powerlmm 0.4.0

May 4, 2018 | 0 Comments

In this post I will show some of the new simulation features that will be available in powerlmm 0.4.0. You can already install the dev version from GitHub. # GitHub devtools::install_github("rpsychologist/powerlmm") The revamped simulation functions offer 3 major new features: Compare multiple model formulas, including OLS models (no random ... [Read more...]

New d3.js visualization: Interpreting Correlations

August 1, 2014 | 0 Comments

Here is a new visualization done in d3js. In this visualization I show a scatter plot of two variables with a given correlation. The variables are samples from the standard normal distribution, which are then transformed to have a given correlation by... [Read more...]
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