Mplus Users Guide v6.. - Muthén & Muthén

MODEL CommandCONSTRAINT statement of the VARIABLE command cannot be usedin MODEL TEST. Model restrictions can be defined using the equalsign (=) and all arithmetic operators and functions that are available inthe DEFINE command with the exception of the absolute value function.Following is an example of how to place restrictions on the parametersin the MODEL and MODEL CONSTRAINT commands using MODELTEST:MODEL:f1 BY y1y2-y6 (p2-p6);MODEL CONSTRAINT:p4 = 2*p2;MODEL TEST:p3 = 0;p6 = .5*p5;where in the MODEL command, p2 represents the factor loading for y2,p3 represents the factor loading for y3, p4 represents the factor loadingfor y4, p5 represents the factor loading for y5, and p6 represents thefactor loading for y6. In the MODEL CONSTRAINT command, thefactor loading for y4 is constrained to be two times the factor loading fory2. In the MODEL TEST command, the factor loading for y3 is fixed atzero and the factor loading for y6 is equal to one half the factor loadingfor y5. The model described in the MODEL and MODELCONSTRAINT commands is tested against the same model except forthe restrictions described in MODEL TEST. A Wald chi-square testwith two degrees of freedom is computed.THE MODEL PRIORS COMMANDThe MODEL PRIORS command is used with ESTIMATOR=BAYES tospecify the prior distribution for each parameter. The default is to usediffuse (non-informative) priors. Following is a table that shows thedistributions available and the default priors for different types ofparameters:619