Use this parameter to list additional variables whose levels form distinct categories in the model .You can then use variables to form Additional Fixed Effects below. Numerical indicator variables containing either 0s or 1s are created for each level of each variable specified here.If you do not specify an effect here, then its numerical values are used directly in the model as in linear regression .Note : The order in which you specify class variables determines how LSMeans and interaction effects are sorted.All of the relevant variables are displayed in the Available Variables field.
Click to add the highlighted variable(s) to the Additional Class Variables field, as shown below:Caution : Specifying a very large number of variables or using a data set with a large number of variables can prohibitively increase the time needed to run this process.