This course is the perfect follow-up to the Basic statistics in R course for people who are doing experiments with multiple grouping variables, dependent groups  and/or mixed designs. Where the Basic statistics in R course ends with a brief description of the use of lm() and lme() for comparing groups, these topics form the starting point for this course. Linear mixed models have rapidly gained popularity in the last 20 years. They became the most used tool in research, particularly in life sciences. Yet, they are often not well understood and misused.This short course will provide the background of the models but will be as applied as possible with examples and R-code.