Re: Mechanisms are Needed to Explain Cohen's Data

[BERNARD L COHEN <blc+@PITT.EDU>]

On Fri, 11 Jan 2002, Kai Kaletsch wrote:



>

> > --Are you suggesting that a treatment is needed for non-smokers

> > living in houses where there are smokers? That would be very difficult in

> > any study.

>

> Actually, I was looking for some reassurance (perhaps by a mathematical

> exercise) that this could not bias your results by much.



	--I could easily treat this with a model

>

> > In case-control studies, they don't ask whether there are other

> > people in the house who smoked.

>

> They don't have to. They actually measure the radon concentration of the

> house and assign it to the occupants.



	--I thought the problem you raised was that the radon progeny are

different for smokers and non-smokers. They don't measure radon progeny.

	Also, they measure radon now and assume it was the same 10-50

years earlier; smoking in the house could have changed during that period.



> You are trying to use the total amount

> of radon in the county and divide it up between smokers and non-smokers.



	--I am not trying to divide it up. I normally assume the same

average radon levels for smokers and non-smokers. In special treatments, I

assume there to be differences and investigate the consequences



> That was my point: plausibility of the correlation depends on the

> plausibility of the mechanism.



	--My treatments of plausibility of correlation are based on the

assumption that there is no strong direct mechanism, and correlations

arise (as they nearly always do) through indirect processes like

socioeconomic factors affecting both radon and lung cancer through

unrelated reasons.



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