The RANDOM statement defines the random effects constituting the vector in the mixed model. It can be used to specify traditional variance component models (as in the VARCOMP procedure) and to specify random coefficients. The random effects can be classification or continuous, and multiple RANDOM statements are possible.
Using notation from the section Mixed Models Theory, the purpose of the RANDOM statement is to define the matrix of the mixed model, the random effects in the vector, and the structure of . The matrix is constructed exactly as the matrix for the fixed effects, and the matrix is constructed to correspond with the effects constituting . The structure of is defined by using the TYPE= option.
You can specify INTERCEPT (or INT) as a random effect to indicate the intercept. PROC MIXED does not include the intercept in the RANDOM statement by default as it does in the MODEL statement.
Table 65.15 summarizes the options available in the RANDOM statement. All options are subsequently discussed in alphabetical order.
Table 65.15: Summary of RANDOM Statement Options
Option 
Description 

Construction of Covariance Structure 

Requests that the matrix be read from a SAS data set 

Varies covariance parameters by groups 

Specifies data set with coefficient matrices for TYPE=LIN 

Eliminates columns in corresponding to missing values 

Indicates that ratios are specified in the GDATA= data set 

Identifies the subjects in the model 

Specifies the covariance structure 

Statistical Output 

Determines the confidence level () 

Requests confidence limits for predictors of random effects 

Displays the estimated matrix 

Displays the Cholesky root (lower) of estimated matrix 

Displays the inverse Cholesky root (lower) of estimated matrix 

Displays the correlation matrix corresponding to estimated matrix 

Displays the inverse of the estimated matrix 

Displays solutions of the Gside random effects 

Displays blocks of the estimated matrix 

Displays the lowertriangular Cholesky root of blocks of the estimated matrix 

Displays the inverse Cholesky root of blocks of the estimated matrix 

Displays the correlation matrix corresponding to blocks of the estimated matrix 

Displays the inverse of the blocks of the estimated matrix 
You can specify the following options in the RANDOM statement after a slash (/).