[R] How to use pakcage SEM

Mitsuo Igarashi mitsu5 at ruby.famille.ne.jp
Wed May 21 02:38:06 CEST 2003

Dear John:

I appreciate the teaching given by the author of the package SEM.

It is a nice paper "appendix-sems.pdf" for me.
And I have found a book "An R and S-PLUS Companion to Applied 
Regression by John Fox". I am going to learn more.

Thank you very much indeed.
Best Regards.
Mitsuo Igarashi
mitsu5 at ruby.famille.ne.jp

John Fox <jfox at mcmaster.ca> wrote:

> Dear Mitsuo,
> At 12:02 AM 5/21/2003 +0900, Mitsuo Igarashi wrote:
> >Hello, Dear John.
> >
> >As you taught me, I obtained the result which I expect and is
> >the same as that of EQS.
> >I have started to learn structural equation modeling. This
> >pushes my understanding SEM. Thank you very much.
> >
> >Would you permit me to ask a question?
> >This EQS program sets an error covariance between V1 and V2.
> >However,It seems to me that the package SEM does not have the
> >method of error covariance. So I set a covariance between V1 and
> >V2. What is the difference between these two settings of
> >covariances?
> Unlike EQS, the sem function uses the "ram" form of a structural-equation 
> model. Setting a covariance between endogenous variables V1 and V2 is 
> interpreted in this form of the model as an error covariance. See 
> <http://www.socsci.mcmaster.ca/jfox/Books/Companion/appendix-sems.pdf> for 
> some more information.
> John

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