R help - Feb 2010 - interpreting error estimate in SEM

hi,

I'm using the sem package, and I want to make sure I'm interpreting the
output correctly. Here is an excerpt of my output. When I report the MWD error,
should I say that 59% of the variation in MWD is not explained by the model, or
that 59% of the variation is explained, or something entirely different.

Parameter Estimates
                   Estimate  Std Error z value  Pr(>|z|)
NplantRoots         0.462029   0.120803   3.82466 1.3095e-04   plantRoots
<--- N
...           
CoError             1.000011 0.151850   6.58553 4.5325e-11 Co <--> Co
carbonateError      1.000009 0.156217   6.40142 1.5394e-10 carbonate  
<--> carbonate
MWDError            0.589788   0.092128   6.40185 1.5351e-10    MWD <-->
MWD

Thanks
Kathryn

Dear Kathryn,

I assume that MWDError is the error variance associated with MWD. If MWD is
a standardized variable (i.e., with a variance of 1) then 59% of its
variance is unaccounted for.

I hope this helps,
 John

--------------------------------
John Fox
Senator William McMaster 
  Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
web: socserv.mcmaster.ca/jfox
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
On
> Behalf Of Kathryn Barto
> Sent: February-09-10 6:23 AM
> To: r-help at r-project.org
> Subject: [R] interpreting error estimate in SEM
> 
> hi,
> 
> I'm using the sem package, and I want to make sure I'm interpreting
the
> output correctly. Here is an excerpt of my output. When I report the MWD
> error, should I say that 59% of the variation in MWD is not explained by
the
> model, or that 59% of the variation is explained, or something entirely
> different.
> 
> Parameter Estimates
>                    Estimate  Std Error z value  Pr(>|z|)
> NplantRoots         0.462029   0.120803   3.82466 1.3095e-04   plantRoots
<--
> - N
> ...
> CoError             1.000011 0.151850   6.58553 4.5325e-11 Co <--> Co
> carbonateError      1.000009 0.156217   6.40142 1.5394e-10 carbonate
<-->
> carbonate
> MWDError            0.589788   0.092128   6.40185 1.5351e-10    MWD
<-->
MWD
> 
> Thanks
> Kathryn
> 
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