Hello sci.stat* readers,

  I have been working with SEMs (actually, the models I've been
working with are just Mixed models) and am curious why SEM 
practitioners seem to assess model fit by only comparing the 
observed and predicted covariance matrices.  As opposed to (also)
using statistics based on observed vs. predicted outcomes.

  One can have an SEM with a covariance matrix that is fit very 
well (or perfectly).  Yet, if you compared the predicted and observed
outcomes, it's terrible!  So, two things:

1.  What is the rationale for ignoring this type of poorly fitting model
    (seems, to me, to be a fundamental flaw - even if you are just using
     if for "exploration")?

2.  Is there software that gives you both kinds of fit statistics?
    LISREL 8.3 and PROC CALIS seems to only give those based on
    predicted and observed covariance matrix.  And PROC MIXED only
    allows certain paramaterizations.

Thanks!

(I am aware of SEMNET, but thought I would ask statisticians first.)


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