The HPMIXED procedure enables you to specify a linear mixed model with variance component structure, to estimate the covariance parameters by restricted maximum likelihood, and to perform confirmatory inference in such models. The HPMIXED procedure fits the specified linear mixed model and produces appropriate statistics.

The following are some of the basic features of the HPMIXED procedure:

• capacity to handle large linear mixed model problems for balanced or unbalanced data

• MIXED-type MODEL and RANDOM statements for model specification and CONTRAST, ESTIMATE, LSMEANS, and TEST statements for inferences

• estimate covariance parameters by restricted maximum likelihood (REML)

• output statistics by using the OUTPUT statement

• computation of appropriate standard errors for all specified estimable linear combinations of fixed and random effects, and corresponding t and F tests

• subject and group effects that enable blocking and heterogeneity, respectively

• NLOPTIONS statement, which enables you to exercise control over the numerical optimization

The HPMIXED procedure uses the Output Delivery System (ODS), a SAS subsystem that provides capabilities for displaying and controlling the output from SAS procedures. ODS enables you to convert any of the output from the HPMIXED procedure into a SAS data set. See the section ODS Table Names and Chapter 20, Using the Output Delivery System, for further information about using ODS with the HPMIXED procedure.