Statistics

One thing that I always felt uncomfortable in multilevel modeling (MLM) is the concept of a unit-specific (US)/subject-specific model vs. a population-average (PA) model. I’ve come across it several times, but for some reason I haven’t really made an effort to fully understand it.

Data in behavioral research usually follow a clustered structure, such as students nested in schools, participants nested in intervention groups, siblings within families, and, in longitudinal studies, repeated measures nested within persons. In this …