[R] path analysis

[John Fox]

Dear Manuel and list,

I see that I wrote "point-biserial" when I meant "biserial."

Sorry,
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of John Fox
> Sent: Sunday, August 14, 2005 1:34 PM
> To: 10133msb at comb.es
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] path analysis
> 
> Dear Manuel,
> 
> Polychoric correlations imply only that the *latent* 
> variables are continuous -- the observed variables are 
> ordered categories. Tetrachoric and point-biserial 
> correlations are special cases respectively of polychoric and 
> polyserial correlations. As long as you're willing to think 
> of the dichotomous variable as the dissection into two 
> categories of a latent continuous variable (and assuming 
> multinormality of the latent variables), you can use the 
> approach that I suggested. This isn't logistic regression, 
> but it's similar to a probit model.
> 
> Regards,
>  John
> 
> --------------------------------
> John Fox
> Department of Sociology
> McMaster University
> Hamilton, Ontario
> Canada L8S 4M4
> 905-525-9140x23604
> http://socserv.mcmaster.ca/jfox
> -------------------------------- 
> 
> > -----Original Message-----
> > From: r-help-bounces at stat.math.ethz.ch 
> > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Manel Salamero
> > Sent: Sunday, August 14, 2005 12:34 PM
> > To: r-help at stat.math.ethz.ch
> > Subject: Re: [R] path analysis
> > 
> > This solves part of my problem with the independent ordinal 
> variables, 
> > but my dependent variable is truly categorial (illness/no illness). 
> > Polychoric correlation implies that data are continuous, 
> which in not 
> > the case. Is possible to implement logistic regression in the path 
> > model?
> > 
> > Thanks,
> > 
> > Manel Salamero
> > 
> > ---------- Original Message ----------------------------------
> > De: "John Fox" <jfox at mcmaster.ca>
> > Data:  Sat, 13 Aug 2005 19:35:24 -0400
> > 
> > Dear Manel,
> > 
> > > -----Original Message-----
> > > From: r-help-bounces at stat.math.ethz.ch 
> > > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of
> > SALAMERO BARO,
> > > MANUEL
> > > Sent: Saturday, August 13, 2005 2:02 PM
> > > To: r-help at stat.math.ethz.ch
> > > Subject: [R] path analysis
> > > 
> > > Someone knows if it is possible to perform a path 
> analysis with sem 
> > > package (or any other) to explain a dependent
> > > *dichotomus* variable?
> > > 
> > 
> > Yes -- you can use the hetcor() function in the polycor package to 
> > generate a correlation matrix and boot.sem() in the sem 
> package to get 
> > standard errors or confidence intervals. Make sure that the 
> > dichotomous variables are represented as factors. See 
> ?boot.sem for an 
> > example.
> > 
> > I hope this helps,
> >  John
> > 
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