Mixed Models

Introduction to Random Effects Models, Including HLM

Hierarchical linear models — also known as mixed models, multilevel models, and random effects models — are now common in the social sciences. Their popularity stems from the frequency with which analysts encounter data that are hierarchically structured in some manner. Employees may be nested within firms, students within schools, or voters within districts. There may even be multiple observations taken on a single individual that can be considered to be nested within that person.
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