

Adding indicator residuals to a regre... 

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Joe Crozier posted on Wednesday, July 18, 2007  11:21 am



Hi, I am trying to respond to a reviewer's comment on a paper. I have been asked to estimate a twogroup model in which an observed variable (Y) is regressed on a latent factor (F) which has six indicators (X1X6). In addition, I have been asked to add the residuals of X1X6 into the regression as well. I am not sure how to code this or if this is even identified. My initial attempt at a model statement is below: Model: F by X1X6; Y on F X1X6; Model Group2: F by X2X6; Y on F X1X6; Is this correct? Thanks! Joe 


Saying "y on x1x6" will regress y on the x variables themselves, not their residuals in the factor model. You have to define a factor corresponding to each residual and regress on those factors. And, delete the usual residual so you don't get two per indicator. So say, f by x1x6; x1x6@0; ! deleting the usual residual var fx1 by; ! this will be a new residual fx2 by;  fx6 by; fx1 with fx2fx6@0; !zero res covs fx2 with fx3fx6@0; etc fx1fx6 with f@0; x1 on fx1@1; ! this adds the new residual ! to x1  x6 on fx6@1; y on f fx1fx6; I think that should work. 

Joe Crozier posted on Wednesday, July 18, 2007  3:49 pm



Hi, Thanks for the help. I tried to implement this approach, but I received an error indicating that the model may not be identified. Here is the model statement that I used: ASB by ly12ext abq12 a12agg sip2 sip4 sip5: ly12ext@0; abq12@0; a12agg@0; sip2@0; sip4@0; sip5@0; fx1 by; fx2 by; fx3 by; fx4 by; fx5 by; fx6 by; fx1 with fx2fx6@0; fx2 with fx3fx6@0; fx3 with fx4fx6@0; fx4 with fx5fx6@0; fx5 with fx6@0; fx1fx6 with ASB@0; ly12ext on fx1@1; abq12 on fx2@1; a12agg on fx3@1; sip2 on fx4@1; sip4 on fx5@1; sip5 on fx6@1; ev01hrNO on ASB fx1 fx2 fx3 fx4 fx5 fx6 ; Does this look right? Thanks, Joe 


I don't see a problem off hand, so you'd better send the input, output, data, and license number to support@statmodel.com for further scrutiny. 

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