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标题: Feifei 94 请教 [打印本页]

作者: victoria820 时间: 2010-4-4 21:07 标题: Feifei 94 请教

94. 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 people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.

A reasoning error in the argument is that the argument

(A) attempts to infer a value judgement from purely factual premises

(B) attributes to every member of the population the properties of the average member of the population

(D) ignores the fact that some cocaine users do not test positive

(E) advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine

这题的答案应该是什么呀？我选的是A。有没有人愿意帮我解答一下。

作者: catmice 时间: 2010-4-5 00:34

你选A的理由是什么？

作者: fangzep 时间: 2010-4-5 07:36

A is wrong because argument deduces the conclusion based on 2 data inputs. Majority is not a "value" judgement since it is more of a percentage, over 50%.

B is wrong the argument never talked about "average member"

C is correct, if the total poluation contains for example 99% non-cocaine user and only 1% of user, the majority of those tested positive could be people who never used cocaine. This, C contradicts argument,s conclusion.

作者: jianglxiang 时间: 2010-4-5 21:57

Thank you for the clarification.

作者: franker 时间: 2010-4-6 21:02

question for C. the problem says" the vast... the vast"

for a given percentage of ppl who use cocaine, no matter the sample size, the percentage of ppl who tested positive and use cocaine is a constant. right?

作者: GlendaKuo 时间: 2010-4-12 20:34

谢谢你的解释。
我当时看了答案都没有想明白是为什么。
FEIFEI。。。。。。真让人伤心。

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