Will_Pearson comments on Science Isn't Strict Enough - Less Wrong

13 Post author: Eliezer_Yudkowsky 16 May 2008 06:51AM

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Comment author: Will_Pearson 16 May 2008 07:36:20AM -2 points [-]

"Contrast this to the notion we have in probability theory, of an exact quantitative rational judgment. If 1% of women presenting for a routine screening have breast cancer, and 80% of women with breast cancer get positive mammographies, and 10% of women without breast cancer get positive mammographies, what is the probability that a routinely screened woman has breast cancer? 7.5%. You cannot say, "I believe she doesn't have breast cancer, because the experiment isn't definite enough." You cannot say, "I believe she has breast cancer, because it is wise to be pessimistic and that is what the only experiment so far seems to indicate." 7.5% is the rational estimate given this evidence, not 7.4% or 7.6%. The laws of probability are laws."

What is the probability that whatever methods you use to determine whether someone has breast cancer in this case are 100% correct?

We do not live in a maths problem, data can be bad.