Re: NY Times on breast cancer rates

[William Prestwich <prestwic@MCMAIL.CIS.MCMASTER.CA>]

The article on breast cancer rates got me curious about something. The

numbers were quoted to 4 figure accuracy, and no standard deviations or

whatever were given. What got me curious was how you would ever assign

one given the uncertainty associated with the variability in diagnostic

success. Up to now I had simply not thought things through because in

so many nuclear studies, when categorized the numbers involved are

so small that I assumed Poisson statistics was dominant. This is surely

important. Many radsafers have correctly commented that in any collection

of values there will be many above the mean so that a higher value doesn't

necessarily reflect anything significant. All this is only meaningful with

a reasonably accurate knowledge of the distribution, or at the very least,

its variance.

bill Prestwich

McMaster University,

Hamilton, Ontario.





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