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Re: Fwd: Re: Cohen's Fallacy
I have had great difficulty in getting this message to
radsafe - please take into account my first message -
I think it is most relevant to the discussion of
radon.
Enjoy - Tom
--- Thomas J Savin <tjsav@lycos.com> wrote:
> Apologies galore - its just that I did not receive
> my message from radsafe - so I am sending it out
> again. I think my message speaks for itself. There
> is definitely a point for which I address.
> ---
> Tom Savin
>
> --------- Forwarded Message ---------
>
> DATE: Sun, 27 Jan 2002 18:06:55
> From: "Thomas J Savin " <tjsav@lycos.com>
> To: "Rad health" <healthrad@HOTMAIL.COM>
>
> It seems to me that some of this scientific debate
> is concerned with Type I and type II errors. In
> other words, does one subscribe statistically to
> whether or not they are biased to avoid a false
> positive vs a false negative result. Which camp do
> they support? Any Comments? Tom
> ---
> Tom Savin
>
> On Sun, 27 Jan 2002 16:21:20
> Rad health wrote:
> >After reading the epidemiologic technique in the
> paper Dr. Field suggested
> >to Dr. Cohen, I think it could possibly help to
> correct the problem with
> >Cohen's analyses pointed out here by Doll and
> Darby. This is the same
> >problem Field pointed out previously of the radon
> varying more within county
> >than between counties. The variance of smoking
> within county co-correlates
> >with other factors that Cohen has not been able to
> treat at the within
> >county level.
> >
> >Don
> >
> >J. Radiol. Prot. 20 (June 2000) 221-222
> >
> >LETTER TO THE EDITOR
> >
> >Reply to `Explaining the lung cancer versus radon
> exposure data for USA
> >counties'
> >
> >Sarah Darby and Richard Doll
> >Clinical Trial Service Unit, University of Oxford,
> Nuffield Department of
> >Clinical Medicine, Harkness Building, Radcliffe
> Infirmary, Oxford OX2 6HE,
> >UK
> >
> >Professor Cohen states in his letter that his
> analysis `encompasses all of
> >the Doll suggestions'. It is, however, logically
> impossible for it to have
> >done so using data at the level of counties. This
> is because the effect of
> >cigarette smoking on the relationship between
> residential radon and
> >individual lung cancer risk will be determined by
> the relationship between
> >smoking status and lung cancer among the
> individuals within each county.
> >Unless smoking is irrelevant to lung cancer risk
> (which we know to be
> >untrue) or smoking status and residential radon are
> uncorrelated within each
> >county (which seems unlikely), the relationship
> between residential radon
> >and lung cancer at the county level will differ
> from that at the level of
> >the individual in a way that cannot be overcome by
> including corrections for
> >smoking habits at the county level, even if these
> corrections correctly
> >represent the smoking habits of the individuals
> within each county. The
> >difference in the relationship between a risk
> factor and a disease rate at
> >the level of the individual and at an area level is
> the ecologic fallacy and
> >is described in detail by Greenland and Robins
> (1994) and Morgenstern
> >(1998). Lubin (1998) has also demonstrated that
> biases caused by the
> >ecologic fallacy can be of any magnitude from minus
> infinity to plus
> >infinity.
> >
> >In two recent studies (Lagarde and Pershagen 1999,
> Darby et al 2000),
> >parallel individual and ecological analyses have
> been carried out of
> >identical data from case-control studies of
> residential radon (Peshagen et
> >al 1994, Darby et al 1998). These analyses have
> shown that, in addition to
> >any bias caused by the ecological fallacy,
> ecological studies of residential
> >radon and lung cancer are also prone to biases
> caused by determinants of
> >lung cancer risk that vary at the level of the
> ecological unit concerned. In
> >these two examples, the additional variables were
> latitude and urban/rural
> >status respectively. The explanation of these
> variables is not yet well
> >understood and they may well be, in part, surrogate
> measures for some
> >aspects of the subjects' smoking history not
> accounted for by the measures
> >of smoking status that have been derived from the
> individual questionnaire
> >data and used in the analysis of the data for
> individuals. They had only a
> >minor effect on analysis at this level but a
> substantial effect on the
> >ecological analyses. The presence of these
> variables is further evidence of
> >the pitfalls of ecological studies.
> >
> >
> >
>
>_________________________________________________________________
> >Chat with friends online, try MSN Messenger:
> http://messenger.msn.com
> >
>
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