Using SAS PROC MIXED to demystify the hierarchical linear model

Hierarchical data analyses in different disciplines are reviewed to compare statistical applications of the Hierarchical linear Model (HLM) software and the SAS MIXED procedure. Similar features of the 2 programs are illustrated through use of the SAS MIXED procedure to confirm an HLM example. The SAS is a standard statistical package with a large group of users; discussions of the shared features in statistical computing may identify options to demystify existing methods for analyzing hierarchical data.