Linear Mixed Models
http://mfviz.com/hierarchical-models/
https://github.com/mkfreeman/hierarchical-models/
https://andrewgelman.com/2017/11/12/fitting-multilevel-models-predictors-group-effects-correlate/
https://stats.idre.ucla.edu/other/mult-pkg/introduction-to-linear-mixed-models/
https://web.stanford.edu/class/psych252/section/Mixed_models_tutorial.html
https://web.stanford.edu/class/psych252/section_2013/Mixed_models_tutorial.html
https://ourcodingclub.github.io/2017/03/15/mixed-models.html
https://stats.idre.ucla.edu/r/dae/mixed-effects-logistic-regression/
https://pagepiccinini.com/r-course/
https://www.jaredknowles.com/journal/2013/11/25/getting-started-with-mixed-effect-models-in-r
http://edwardlib.org/tutorials/linear-mixed-effects-models