Re: Confounders and Coincidences

["Otto G. Raabe" <ograabe@UCDAVIS.EDU>]

At 03:52 PM 5/8/03 +0000, Bill Field wrote:

>Dr. Cohen wrote - 

>

>Unfortunately, ecological control of a covariate contributing to ecologic

bias 

>is generally inadequate to remove the bias produced by the covariate even in 

>the absence of measurement error. 

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May 8, 2003



Dear Bill:



Thanks for your comment. You bring up an important point. 



But it seems to me that the fact that ecological control may not remove the

bias does not mean that it never helps. If all you have is ecological data,

isn't testing the effect of ecological control a useful exercise?



Otto



**********************************************

Prof. Otto G. Raabe, Ph.D., CHP

Center for Health & the Environment

(Street Address: Bldg. 3792, Old Davis Road) 

University of California, Davis, CA 95616

E-Mail: ograabe@ucdavis.edu

Phone: (530) 752-7754   FAX: (530) 758-6140

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