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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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> >

> 

> 

> 

> 





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