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path analysis (misspecification?)

1 message · William Revelle

#
Martin,
If you examine the residuals
  mod1 <- sem(p.model,cov.matrix,N=422)
residuals(mod1)

You will see that you are completing ignoring the y1-x2 covariance.

When you examine your covariance matrix as a correlation matrix,
r.mat <- cov2cor(cov.matrix)
  you will note that the  x2-y1 relationship is very large (the 
correlation is -.65)

Your original model was fully saturated and what you are reporting is 
actually what I label as p.model which is your full model without the 
last row.

If you compare the fully saturated model with your  mod1, you will 
find that the reason for the  large chi square is due to not 
specifying the x2-y1 path.

You might want to read some more on sem techniques.  A good 
introduction is a text by John Loehlin.

Bill