Adding constraints improved fit in ne... PreviousNext
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 Ads posted on Tuesday, October 29, 2013 - 8:39 pm
I have run 2 path analysis models, where I constrained a few parameters to 0 in the second model. As expected, the chi-square and SRMR worsened slightly, but the CFI and RMSEA actually improved slightly when adding constraints. Is this possible or reflective of a common error? I have pasted both models and some corresponding fit index results below (where the only differences between the 2 models are the constraints are added to relationships when predicting Y2 and Y4). Thank you!

Model 1 - Fewer constraints

MODEL:
Y1 ON X1 X2;
Y2 ON X1 X2;
Y3 ON X3 X4;
Y4 ON X3 X4;
X1 WITH X3@0 X4@0;
X3 WITH X2@0;

Loglikelihood
H0 Value -2324.189
H1 Value -2318.040

Chi-Square Test of Model Fit 12.298
RMSEA 0.028
CFI 0.981
TLI 0.962
SRMR 0.062


Model 2 - Added constraints

MODEL:
Y1 ON X1 X2;
Y2 ON X1@0 X2@0;
Y3 ON X3 X4;
Y4 ON X3@0 X4@0;
X1 WITH X3@0 X4@0;
X3 WITH X2@0;

Loglikelihood
H0 Value -2324.949
H1 Value -2318.040

Chi-Square Test of Model Fit 13.817
RMSEA 0.000
CFI 1.000
TLI 1.025
SRMR 0.068
 Bengt O. Muthen posted on Tuesday, October 29, 2013 - 10:49 pm
It is not an error that constraining some parameters can give a better CFI and RMSEA.
 Ads posted on Wednesday, October 30, 2013 - 12:33 pm
Thank you!
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