

Moderated factor loadings 

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Hello, I apologize if I have missed the answer to this topic in an earlier post. I would like to allow a factor loading to be moderated by a continuous variable (age). I've tried labeling the factor loading (i.e., 'b1') and using the MODEL CONSTRAINTS command to regress the parameter on age: b1 on age. However, I must be doing something wrong because I get the following error: *** ERROR in MODEL command Unknown group name CONSTRAINTS specified in groupspecific MODEL command. Advice on how to do this properly would be much appreciated! 


To moderate the loading b1, you shouldn't regress b1 on age (which implies a residual), but instead express a deterministic relationship. In Model Constraint you would use the NEW parameters a and b, say, and say b1 = a + b*age; where you have stated constraint = age; This estimates a and b, where a is the b1 slope value at age=0 (you may want to center age at its mean for a to be meaningful). 


Thank you! 


Hello, I apologize for another question, but I am still having difficulty with the model that I described earlier. After making the fix that you suggested, age is not recognized in the MODEL CONSTRAINT command. I've tried keeping it on the 'use' command line and removing it, and I've tried using the DEFINE statement to crease a new age variables = 1* the old (centered) age, but neither of these strategies worked. It's not 'NEW' since it's a measured variable. Do you know what I am doing wrong? Thanks again for your help. (Error message pasted below): *** ERROR Unknown parameter label in MODEL CONSTRAINT: AGE_C8 


You should say Constraint=age; in the Variable command. See V6 UG ex 5.23 for an example. If you are centering age, you may have to do this in a first step, saving the data, before the run with Constraint=age. If you are still having problems, send output to support. 

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