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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