Re: st: Re: advice re: "intervening" variable

[Richard Goldstein <richgold@ix.netcom.com>]

Thanks to Sergiy and Austin:

Sergiy:

In this case, at least, it works as I stated because the researchers
force it to work this way -- they give each S a drug that directly
affects blood pressure; the change in blood pressure affects
vessel diameter and, then, heart rate

Thanks to both re: citations

Rich

Sergiy Radyakin wrote:
> Hello Richard,
>
> Google picture search --> "structural model" will give you a lot of 
> examples.
> However "intervening" variable is the one which usually reflects a 
> Concept, like "hunger" or "fear" (lots of examples from the area of 
> psychology).
>
> E.g. here you will find a model of impulse-buying behaviour:
> http://emeraldinsight.com/Insight/ViewContentServlet?Filename=Published/EmeraldFullTextArticle/Articles/2840100404.html 
>
> While "Fashion involvment" and "Impulse buying" are quite real, 
> "positive emotion" is rather hypothesized.
>
> Your "diameter of blood vessel" seems to be quite a real variable though.
> I am not a doctor, but I thought it works the other way around:
> one smokes --> diameter decreases --> pressure increases --> heart rate 
> increases --> one dies ?
>
> Another chain:
> "Moreover, The nicotine in cigarettes and other tobacco products causes 
> your blood vessels to constrict and your heart to beat faster, which 
> temporarily raises your blood pressure. "
> is described here: 
> http://www.highbloodpressuremed.com/smoking-and-high-blood-pressure.html
>
> I wonder how do you establish causality in this case?
>
> ----
> An example from economics (Student Achievement and National Economic
> Growth, Nov 2006): 
> http://www.journals.uchicago.edu/AJE/journal/issues/v113n1/113101/113101.web.pdf 
>
>
> Regards, Sergiy
>
>
>
> ----- Original Message ----- From: "Richard Goldstein" 
> <richgold@ix.netcom.com>
> To: "statalist" <statalist@hsphsun2.harvard.edu>
> Sent: Monday, March 05, 2007 3:57 PM
> Subject: st: advice re: "intervening" variable
>
>
>
> > Hi all:
> >
> > This is more a stat question that a Stata question.
> >
> > I have a system of 3 variables where one variable is in between,
> > in time and physiology, the other two variables:
> >
> > blood pressure -> diameter of blood vessel -> heart rate
> >
> > That is, a change in blood pressure "causes" some change in
> > the diameter of the blood vessel which in turn "causes"
> > some change in heart rate (actually in "RRI" which is,
> > basically, the inverse of heart rate).
> >
> > I have never come across this situation before, but I believe
> > that several substantive disciplines do have such situations.
> >
> > Actually, I have found a fair amount of literature in
> > psychology; a recent overview is MacKinnon, DP, AJ Fairchild,
> > and MS Fritz (2007), "Mediation Analysis", _Annual Review of
> > Psychology_, 58: 593-614
> >
> > I believe that other disciplines might also see such
> > situations, e.g., economics and epidemiology, but have
> > been unable to find any literature.
> >
> > So, is there literature on this in disciplines other than
> > psychology? If so, any citations, esp. overviews, would
> > be greatly appreciated (regardless of whether the cite is
> > to ariticles or books).
> >
> > Thanks,
> >
> > Rich
> >
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