Linear Mixed Models (LMM)— also known as hierarchical linear models, mixed models, multilevel models, and random effects models — are now common in science.
LMM are used whenever you have nested data (i.e., data are collected from multiple individuals in a group or when data is collected multiple times from the say individuals)
Quant Psych: Mixed Models, Hierarchical Linear Models, and Multilevel Models: A simple explanation (18:27)
Mod-U: Introduction to Multi-Level Modeling (4:37)
Mod-U: Random Intercept Multi-Level Models (7:36)
Mod-U: Random Slope Coefficient Multi-Level Models (6:24)
Andy Field: Multilevel models (1:01:01)