请教LSAT-Set15-SecIV-Q13,18

nobody

13. "addiction" has been defined as "dependence on and abuse of a psychoactive substance" Dependence and abuse do not always go hand in hand, however. For example, cancer patients can become dependent on morphine to relieve their pain, but this is not abusing the drug. Correspondingly, a person can abuse a drug without being dependent on it. Therefore, the definition of "addiction" is incorrect.

The relevance of the example of cancer patients to the argument depends on the assumption that

(A) cancer patients never abuse morphine

(B) cancer patients often become dependent on morphine

(C) cancer patients who are dependent on morphine are addicted to it

(D) cancer patients who abuse a drug are dependent on it

(E) cancer patients cannot depend on morphine without abusing it

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答案C, 不太明白问题的意思，好像不是问结论成立所需的假设，请大家指教。

18. According to government official involved in overseeing airplane safety during the last year, over 75 percent of the voice-recorder tapes taken from small airplanes involved in relatively minor accidents record the whistling of the pilot during the fifteen minutes immediately preceding the accident. Even such minor accidents pose some safety risk. Therefore, if passengers hear the pilot start to whistle they should take safety precautions, whether instructed by the pilot to do so or not.

The argument is most vulnerable to criticism on the grounds that it

(A) accepts the reliability of the cited statistics on the authority of an unidentified government official

(B) ignores the fact that in nearly one quarter of these accidents following the recommendation would not have improved passenger' safety

(C) does not indicate the criteria by which an accident is classified as "relatively minor"

(D) provides no information about the percentage of all small airplane flights during which the pilot whistles at some time during that flight

(E) fails to specify the percentage of all small airplane flights that involve relatively minor accidents
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答案D，不知A为何错，感觉E也比D好，知道D但不知the percentage of all small airplane flights that involve relatively minor accidents，还是无法判断结论，为何选D？请大家指教。

mindfree

1. 既然说了cancer patient的例子反驳关于addition的定义, 其前提必然是cancer patient addited to morphine. 否则此例无效.

2. 如果90%的flight中pilot都whistle, 远结论就错. 所以此项信息于结论十分关键, 不给不行. A错在数据并不是主要问题. E无关.

nobody

1.问的是例子成立的假设?
2.为何90%的flight中pilot都whistle, 原结论就错? 知道90％航班飞行员吹口哨,但不知多少航班有事故，就不知道吹口哨在事故航班中的比例，还是无法判断结论？请多指教。

mindfree

1. 你对C取非,既cancer patient没有addiction, 原结论是否成立? 原结论是cancer patient的例子说明addiction不一定是abuse drug. 如果cancer patient并没有addiction, 此例作用为何?

2. 原结论为口哨导致accident. 举个例子: 一年一共10000 flights, 其中有100起minor accidents. 如果10000次飞行中, 9000次pilot都吹口哨, 原结论就不成立. 但如果就那75次accident中吹了, 原结论成立. 所以D中的information is critical in evaluating the conclusion. Without this piece of info, the conclusion is unfounded.

nobody

举个例子: 一年一共10000 flights, 其中有100起minor accidents. 如果10000次飞行中, 9000次pilot都吹口哨, 原结论就不成立. 但如果就那75次accident中吹了, 原结论成立.

同意你举的例子,但D只给了所有飞行吹口哨的比例,比如你例子中的9000(90％),但没有给出事故飞行的比例,比如例子中的100(1%),还是无法判断.因为我们不知道事故飞行的比例,可意是1%(100),可意是90%(9000),前者结论不成立,后者结论成立.
E倒是给出事故飞行的比例,再加上提干中的事故飞行中吹口哨的比例,可作出大致判断.
还是不明白为何选D.
谢谢mindfree的解答, 好像你马上要考试,就别浪费宝贵时间解答了,考试后有空给看看.祝考试顺利!

mindfree

你解释一下E如何能推出. 你如果知道5%的flight有accident, 你的结论是什么, 吹是不是原因?

D. 如果我知道所有的flight中, 包括accident和no accident, 吹的比例是90%, 我足可以推断出吹不是原因, 否则绝大多数的flight都会出问题, 不符合common sense. 如果此比例是10%, 很有可能是主要原因.

nobody

5%的flight有accident,我的结论是超过3.75%低于5％的flight有accident也有口哨,能否判断没有统一标准，自己感觉risk程度吧。 D正确是要引用common sense,飞行事故率很低，否则无法判断。
有点困惑，根据题中所给的信息作题不够，还要加上common sense? 可有时用common sense会和题中信息冲突，拿不准用common sense 尺度。
明白了，谢谢mindfree的耐心解答。