Mixed models

Abstract

This document aims at providing a first and basic introduction to the implementation of mixed models in R. We use an applicative example coming from the APEX project, studing the impact of a cognitive program. There might be many ways to study this dataset, and uncountable models that could be defined, keep in mind that the following are just illustrative examples. Although various R packages are available to fit mixed models, which are widely studied objects (still an active research topic), the most famous is probably lme4. The syntaxe is pretty straightforward and the implementation is powerfull. Actually, the full presentation of the package is way beyond the scope of the present workshop. You can find the full documentation here: https://cran.r-project.org/web/packages/lme4/lme4.pdf. Besides, here is an additional (and awesome) reference to go (way) further on mixed models with R: https://m-clark.github.io/mixed-models-with-R/.