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 Posted: Thu Jul 12, 2007 9:54 pm
Okay, we were looking at an example in my text book, which was on how people often incorrectly use probabilities. This is the example given (as near as I can remember it)
A man is taken to court because, from his tax records, it is believed he has commited tax fraud. He declares that he is not guilty of the crime.
Statistics are given showing that 5% of people commit tax fraud, and that only 1% of innocent peoples records will match those of the guilty 5%.
The prosecutors then tell the jury that this shows that there is only a 1% chance that he is innocent.
So anyway, what's wrong with this example and what is the correct probabilty that he is innocent?
((I know the answers by the way))
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Posted: Thu Jul 12, 2007 9:57 pm
6 out of every 100 people have records that look like tax fraud. 5 of those people are likely to have commited the crime, and 1 of those people is likely not to have committed it. In reality, he has about a 17% chance of being innocent.
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Posted: Thu Jul 12, 2007 10:12 pm
CodeLabMaster 6 out of every 100 people have records that look like tax fraud. 5 of those people are likely to have commited the crime, and 1 of those people is likely not to have committed it. In reality, he has about a 17% chance of being innocent. I give you half marks, but your answer is not correct. Your answer is slightly off the actual answer. Good try almost there
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Posted: Thu Jul 12, 2007 10:16 pm
My bad, read the question wrong; about 15.9664%. Hows that?
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Posted: Mon Jul 16, 2007 3:39 pm
YAH!!! Yes, that is the correct answer.
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Posted: Tue Jul 17, 2007 3:57 am
Eh, I don't like the assumption that all guilty people will have records that make them look guilty.
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Posted: Tue Jul 17, 2007 7:55 pm
Well you don't have to, but it never gave any probabilitys for guilty people whose records make them look innocent, so you have to assume it doesn't happen.
Though in reality the reasons why some people who are innocents records make the look guilty would also make some guilty people look innocent.
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Posted: Wed Jul 18, 2007 6:23 am
It changes the answer, so I think it ought to have been given. >_>
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Posted: Thu Jul 19, 2007 10:35 pm
Well, don't blame me. I didn't write the question.
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