Duncan Smith <[EMAIL PROTECTED]> wrote in message
news:9i4e4j$qjm$[EMAIL PROTECTED]...
>
> Sylvia J. Hysong, Ph.D. <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]...
> > Hello,
> >
> > I'm hoping someone can help me with this. I have looked at a
> > multitude of resources including the David Kenny page, this and other
> > newsgroups, Pedhazur (1982), Cohen & Cohen (1983), and Darlington
> > (1990?), to no avail. I am hoping someone can direct me to the right
> > resource. I am trying to conduct a test of double mediation. In
> > other words, I am trying to test the hypothesis that x-->z1-->z2-->y.
> > Is there a way to do this (and if so, what is it?), or must I result
> > to a path analysis or a structural equation model?
> >
> > Thanks in advance for any help.
>
> If I understand the question correctly, this implies a number of
conditional
> independence relationships which can be tested. i.e. x cond. ind. of z2
and
> y given z1; x and z1 cond. ind. of y given z2; x cond. ind. of y given z1
> and z2. If these, and only these, independence relationships hold then
you
> have either x-->z1-->z2-->y or x<--z1<--z2<--y. To decide which, you need
> some background knowledge or to conduct an experiment. You might want to
> check out links at http://www.cs.berkeley.edu/~murphyk/Bayes/bnsoft.html
>
>
Brain not quite in gear. You could also have x<--z1-->z2-->y or
x<--z1<--z2-->y. i.e. all 4 directed graphs are Markov equivalent.
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