Mplus Users Guide v6.. - Muthén & Muthén

Special Modeling Issuesequal to each other. Note that only one equality constraint can bespecified per line.Following is another example of how to specify across group equalityconstraints in the overall MODEL command:MODEL:f1 BY y1-y5;y1-y5 (1);By placing a one in parentheses after the list of residual variances, y1through y5, the values of those parameters are held equal to each otherand across groups. If the five residual variances are free to be estimatedacross the three groups, there are fifteen parameters. With the equalityconstraint, one parameter is estimated.Following is an example of how to specify an equality constraint in agroup-specific MODEL command:MODEL g2: y1-y5 (2);In the group-specific MODEL command for g2, the residual variances ofy1 through y5 are held equal for g2 but are not held equal to the residualvariances of any other group because (2) is not specified in the overallMODEL command or in any other group-specific MODEL command.One residual variance is estimated for g2.Following is an example of how to relax an equality constraint in agroup-specific MODEL command:MODEL g3:y1-y5;In this example, by mentioning the residual variances in a group-specificMODEL command, they are no longer held equal to the residualvariances in groups 1 and 3. Five residual variances are estimated forg3.The overall and group-specific MODEL commands discussed above areshown and interpreted together below:MODEL:f1 BY y1-y5;y1-y5 (1);427