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American Journal of Epidemiology Vol. 152, No. 4 : 393-396
Copyright © 2000 by The Johns Hopkins University School of Hygiene and Public Health

LETTERS TO THE EDITOR

RE: "PRESENTING STATISTICAL UNCERTAINTY IN TRENDS AND DOSE-RESPONSE RELATIONS"

Douglas Easton and Julian Peto

CRC Genetic Epidemiology Unit Strangeways Research Laboratory Worts Causeway Cambridge CB1 8RN, United Kingdom
Section of Epidemiology Institute of Cancer Research 15 Cotswold Road Belmont SM2 5NG, United Kingdom


   INTRODUCTION
 
The recent commentary by Greenland et al. (1Go) criticizes the "floating absolute risk" (FAR) method for presenting uncertainty in estimates of polytomous exposures. However, it then goes on to proose "floating trends," which are exactly the same, to within a constant!

The criticism that Greenland et al. raise of the FAR confidence intervals is that they are not, directly, confidence intervals for the relative risk estimates for each category relative to the baseline category. This is obviously true–they are not meant to be. The whole point of the FAR method is to allow computation of confidence limits for relative risks for any pair of categories. The variance of the log relative risk is obtained by adding the "floating variances" for the two categories, in exactly the same way as one does in, for example, an unpaired t test.

Standard confidence intervals do not provide the same information. This is . . . [Full Text of this Article]


   REFERENCES
 
Sander Greenland, Karin B. Michels, Charles Poole and Walter C. Willett

Department of Epidemiology UCLA School of Public Health 22333 Swenson Drive Topanga, CA 90290
Strangeways Research Laboratory Worts Causeway Cambridge CB1 8RN, United Kingdom
Department of Epidemiology School of Public Health University of North Carolina Chapel Hill, NC 27599-7400
Channing Laboratory Harvard Medical School Boston, MA 02115


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This article has been cited by other articles:


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 Am J EpidemiolHome page
P. G. Arbogast
Performance of Floating Absolute Risks
Am. J. Epidemiol., September 1, 2005; 162(5): 487 - 490.
[Abstract] [Full Text] [PDF]

Home page
 Am J EpidemiolHome page
D. Easton, J. Peto, S. Greenland, K. B. Michels, C. Poole, and W. C. Willett
RE: "PRESENTING STATISTICAL UNCERTAINTY IN TRENDS AND DOSE-RESPONSE RELATIONS"
Am. J. Epidemiol., August 15, 2000; 152(4): 393 - 394.
[Full Text] [PDF]