Re: Genetics prob from book that I cant get (probability type)
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um this sounds really simple? its 50/50 to have it or not, and 67/33 to express it or not, so 33% of 50?
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this is what the book did, and perhaps im reading too much into it, but this was not my answer
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I had better get this right, about half my genetics exam was this type of problem. Give me a second to work it out.
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Yes, the answer is 1/4 that he is afflicted. This is a Bayes problem. The way you do it is, first you assign the prior probabilities, which in his case are 1/2 that he is affected and 1/2 that he isn't. Then you adjust them accordingly. The conditional probability is 1/3 that he will be a carrier and not show symptoms, and 1/1 that he will not be a carrier and not show symptoms. So, your joint probabilities are 1/6 and 3/6. Thus, your posterior probability is (1/6)/(1/6+3/6) = 1/4.
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