A MODEL statement signifies the beginning of a model specification block and designates a model number for the model. All main and subsidiary model specification statements after a MODEL statement belong in that model until another MODEL or GROUP statement is encountered.

The MODEL statement itself does not serve the purpose of model specification, which is actually done by the main and subsidiary model specification statements that follow it. The MODEL statement serves as a "place-holder" of specification of a single model. It also makes the reference to a model easier with an assigned model number. For example, consider the following statements:

   proc tcalis;
      group 1 / data=women_data;
      group 2 / data=men_data;
      model 1 / group=1 label='Women Model';
         {model 1 specification here}
      model 2 / group=2 label='Men Model';
         {model 2 specification here}
      run;

This example illustrates a two-group analysis with two models. One is model 1 labeled as 'Women Model' in a MODEL statement. Another is model 2 labeled as 'Men Model' in another MODEL statement. The two groups, group 1 and group 2, as defined in two separate GROUP statements, are fitted by model 1 and model 2, respectively, as indicated by the GROUP= option of the MODEL statements. Within the scope of model 1, you provide model specification statements by using the main and subsidiary model specification statements. Usually, one of the following main model specification statements is used: FACTOR, LINEQS, LISMOD, MSTRUCT, PATH, RAM, or REFMODEL. Similarly, you provide another set of model specification statements within the scope of model 2.

Hence, for an analysis with a single group, the use of the MODEL statement is not necessary because the model that fits the group is unambiguous.

You can set model-specific options in each MODEL statement. All but two of these options are also available in the PROC TCALIS statement. If you set these options in the PROC TCALIS statement, they will apply to all models, unless you respecify them in the local MODEL statements. If you want to apply some options only to a particular model, set these options in the MODEL statement corresponding to that model.

You can also set group-specific options in the MODEL statement. These group options will apply to the groups that are specified in GROUP= option of the MODEL statement. See the section Options Available in the GROUP and PROC TCALIS Statements for a detailed descriptions of these group options.