RE: Risks of low level radiation - New Scientist Article

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

On Fri, 7 Dec 2001, Jim Nelson wrote:



> I understand the meaning of r-sqaured very well.  I do not see in the

> reference provided that you addresses this issue at all?  Jim



     --As a more concrete example, consider lung cancer rates vs smoking

prevalence for U.S. States. There is little uncertainty in the former as

there was a good survey by the U.S. Census Bureau. The regression gives

R-squared  only 46%, but the slope differs from zero by 6.4 standard

deviations. If we ignore Utah which is very much an outlier but

contributes very few data points to our study of counties, R-squared is

only 36%, but the slope of the regression differs from zero by 5.1

standard deviations.

	If you are expecting R-squared to be 85%, you don't understand the

meaning of R-squared



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