What is the value of prob(conclusion C1 is true IF premise P1 is true)? It depends on the prior probability that the suspect's DNA would be found at the crime scene -- which makes it a true match for some crime scene DNA -- and the true and false positive rates for the police forsensics lab reports for DNA matches. Suppose the prior probability that the suspect's DNA would be found at the crime scene is 0.10.* Suppose the true positive rate for the police forensics lab reports for DNA matches is 0.999. Finally suppose that the false positive rate is 0.005.**(adsbygoogle = window.adsbygoogle || []).push({});

Enter answer as number in box below. Number should be rounded to two decimals (eg 1.00, 0.99, 0.50, 0.00)

*We are sure of ten suspects based on evidence other than the DNA match. There is no more evidence for one than the other. The crime is one where the suspect would inevitably leave something containing his or her DNA.

**We have information or facts from testing about the false positive rate for some labs. This includes the lab that did DNA matching in the O J Simpson murder case. These numbers are representative. We do not have information about the true positive rate. These numbers are guesses.

P1 IS: The forensic lab says "This suspect's DNA matches some of the crime scene DNA"

C1 IS: The suspect's DNA matches some of the crime seen DNA.

The answer is 0.96 or 96%. Normally I can work backwards to find out how the answer is found, but I am totally confused and lost on this one. Been going at it for an hour. This is from a practice quiz, btw, so you are only helping me prepare for a future quiz - not giving me assignment marks or anything.

Thanks

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# Baye's Question: DNA Question

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