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BW2/3 Posted 19 years ago
Grammar

A reasoning error

0 When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast. of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use. the vast majority of those who test positive will be people who have used cocaine.02br
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01b00A reasoning error in the argument02b00 is that the argument02br
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00　　（A） attempts to infer a value judgment from purely factual premises.02br
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00　　（B） attributes to every member of the population the properties of the average member of the population.02br
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00　　（C） fails to take into account what proportion of the population have used cocaine.02br
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00　　（D） ignores the fact that some cocaine users do not test positive.02br
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00　　（E） advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine.02br
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00What do you think answer is?02br
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00I would pick 'a'. Could you explain 'b'? 02br
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00Thank you 0-
  

Top answer

1font 00"When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast. of every 100 people who have used cocaine 99 will test positive.

— Inchoateknowledge

  • 1font 00"When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive.
  • By contrast.
  • of every 100 people who have used cocaine 99 will test positive.
  • Thus, when a randomly chosen group of people is tested for cocaine use.
  • the vast majority of those who test positive will be people who have used cocaine.
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16 Answers
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1font00"When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast. of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use. the vast majority of those who test positive will be people who have used cocaine. "02font02
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0 I don't see any value judgments nor any mention of advocating that people be tested, so I would eliminate A and E immediately.02br
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00 CJ0-
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0I pick "c".02br
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00S.0-
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0 01blockquote
00I pick "c".12blockquote
10That choice seems to have a lot to recommend it, doesn't it!02br
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00 CJ0-
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0"fails to take into account what proportion of the population have used cocaine."02br
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00You do not have to take into account the proportion. The result and the narrow margin of error of the tests reveal the truth.0-
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0"when a randomly chosen group of people is tested for cocaine use 01font00the vast majority of those who test positive02font00 will be people who 01font00have used cocaine02font00." 02br
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00Whether the red part is true is solely determined by the narrow margin of error of tests when
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0 What is your choice, Peter? A, B, C, D, or E?02br
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00 CJ0-
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0When I was learning about "false positives" I think we talked about this - C seems to be the one that fits my recollection of how it was explained to me.0-
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0"c" also sounds good to me after I read a conclusion again. 0-
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0 01blockquote
00"false positives" 12blockquote
10Bayes' Formula. Yes, that's how I remember it too.02br
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00 CJ0-
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