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Topic: WILLYWUTANG & TWO CONDOMS (Read 1184 times) |
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atgdax
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WILLYWUTANG & TWO CONDOMS
« on: Nov 22nd, 2006, 6:47am » |
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how is the 2 condoms 3 women possible ?
and as far as i can tell, in the WILLYWUTANG question- if it is corret 93% then P = 93% .
could it be that easy or am i missing somthing ?
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towr
wu::riddles Moderator
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Some people are average, some are just mean.
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Re: WILLYWUTANG & TWO CONDOMS
« Reply #2 on: Nov 22nd, 2006, 7:17am » |
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on Nov 22nd, 2006, 6:47am, atgdax wrote:and as far as i can tell, in the WILLYWUTANG question- if it is correct 93% then P = 93% .
could it be that easy or am i missing somthing ? |
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You're neglecting the prior probability of 0.001. In the other 0.999 cases the test still gives 93% wrong answer (i.e. saying they're ill when they're not)
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Icarus
wu::riddles Moderator
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Boldly going where even angels fear to tread.
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Re: WILLYWUTANG & TWO CONDOMS
« Reply #3 on: Nov 22nd, 2006, 7:28am » |
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You will find the 2 condoms puzzle in the easy section, and several threads where you can find the answer in the easy forum.
There are also threads for the medium puzzle ("Willywutang has STDs?") wherein you will discover that the 93% value is not correct. Note that the statistics given say that if the person has an STD, 93% of the time the test will come out positive. But the question asked is: if the test comes out positive, what is the probability the person has an STD? This reversing has a profound effect on the probability - particularly given the low likelyhood of having an STD in the first place.
One other thing: We don't have access to know what it is you have been reading. When you post without fully explaining what you are refering to, it makes it extremely difficult for anyone else to have any idea what you are talking about. It took some work on my part to figure out what you meant by the "the WILLYWUTANG question" (willywutang appears in several puzzles here - it's a nickname of the sites creator William Wu).
Please, when posting in reply to a riddle-page riddle, either quote the riddle in the first post, or link to it, so others will know what you are refering to.
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