Jörn Alexander Quent's notebook

where I share semi-interesting stuff from my work

Finding a U-shape with Bayesian interrupted regression

The outset of the problem In one of my project, I’d like to show that there is a U-shape relationship between two variables. The traditional way to do this would be to fit a quadratic model and test whether the quadratic term is different from zero. However, Simonsohn (2018) among other correctly points out that evidence for a quadratic fit is not enough and there might be situations where the quadratic term is not zero but there is no true u-shape. Read more →

Understanding mixed linear models

Preface Note: This is an old post from my early PhD time that I slightly edited but share again because it would be interesting to one or two people. This work documents my attempt to understand the model structure of mixed linear models or multilevel models. I adapted a formula that I found on Wikipedia and work myself through the different models and test whether I am able to retrieve the different parameters with lmerTest. Read more →