mixed models

Understanding levels of variation and mixed models

Data that has some kind of hierarchical structure to it is very common in many fields, but is rarely discussed in introductory statistics courses. Terms used to describe this kind of data include hierarchical data, multi-level data, longitudinal data, split-plot designs or repeated measures designs. Statistical models used for these types of data include mixed-effects models (often abbreviated to just mixed models), repeated measures ANOVA and generalised estimating equations (GEEs).