Parameters | Workflows | Denominator Degrees of Freedom Method

Denominator Degrees of Freedom Method
Use this option to specify the denominator degrees of freedom (DDF) method to be used when random effects are included in the model.
Note: This option is enabled only when a random effect is specified on the Model Variables tab.
The option selected is used for the DDFM= option in the MODEL statement of the MIXED or GLIMMIX procedure. Refer to the SAS PROC MIXED documentation or SAS PROC GLIMMIX documentation for additional details.
Available options are listed in the table below:
Performs the degrees of freedom calculations by inflating the estimated variance- covariance matrix of the fixed and random effects. Satterthwaite-type degrees of freedom are then computed based on this adjustment. By default, the observed information matrix of the covariance parameter estimates is used in the calculations. For covariance structures that have nonzero second derivatives with respect to the covariance parameters, the Kenward-Roger covariance matrix adjustment includes a second-order term. This term can result in standard error shrinkage. Also, the resulting adjusted covariance matrix can then be indefinite and is not invariant under reparameterization.
To Specify a Method for Computing the Denominator Degrees of Freedom Method: