[FRIAM] From My Former Colleague

[David Eric Smith]

The closest thing I can think of, Frank, is Teddy Seidenfeld’s paper Why I am not an Objective Bayesian.

But that is enough of a different position that it could be a derivative title, with quite a different theme.

Eric



> On Jan 7, 2022, at 8:56 AM, Frank Wimberly <wimberly3 at gmail.com> wrote:
> 
> Who wrote a widely cited paper with the title Why I am Not a Bayesian.
> 
> "I have not found on the web any calculation of the probability that you have covid given that you have just decided to take a home covid antigen test and found a positive result.  So I did a couple.
> 
> Abbott Laboratories Rapid antigen covid test (the only one I could get real numbers for):
> 
> "The BinaxNOW test correctly gave a positive result 84.6% of the time compared to PCR. In the same study, the test correctly gave a negative result 98.5% of the time." 
> 
> I will assume that PCR results are ground truth. Assume the base rate of covid infection is 5%--the frequency of infectious covid among people you have come in contact with in the last several days.  Applying Bayes Theorem:
> 
> pr(covid | positive test) = .05 pr(positive test | covid) / pr(positive test) =
> 
> .05 x .846 / (pr (positive test | covid) pr(covid) + pr(positive test | no covid) pr(no covid)) =
> 
> .0423 / (.846 x .05 + .15 x .95)  = .0423 / (.0423 + .1425) = .0423 / .1848 = .2288
> 
> If the base rate of covid infection is 10% the probability of covid given a positive test is 
> 
> .0846 / .0846 +.135 = .3852.
> 
> Bayes say you probably don't have covid. Moral: don't worry but quarantine until you get a negative PCR result."
> 
> 
> ---
> Frank C. Wimberly
> 140 Calle Ojo Feliz, 
> Santa Fe, NM 87505
> 
> 505 670-9918
> Santa Fe, NM
> 
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