prep 1-75再讨论；附上Ron的解释，不懂，请牛牛指教

cician

In the year following an eight-cent increase in the federal tax on a pack of cigarettes, sales of cigarettes fell ten percent. In contrast, in the year prior to the tax increase, sales had fallen one percent. The volume of cigarettesales is therefore strongly related to the after-tax price of a pack of cigarettes.

Which of the following, if true, could most strengthen the argument above?

(A) During the second year after the tax increase, cigarette sales increased by a significant amount.
(B) The information available to consumers on the health risks of smoking remained largely unchanged in the period before and after the tax increase.
(C) Most consumers were unaware that the tax on cigarettes was going to increase.
(D) During the year following the cigarette tax increase, many consumers had less income, in inflation-adjusted dollars, than they had had in the previous year.
(E) During the year after the tax increase, there was a greater variety of cigarettes on the markey than there had been during the previous year.

答案是B，对于B没有疑问；想不通这个C。在manhattan上看到了跟我想的一样的一个提问：

Doesn't choice C also eliminate a potential cause to the effect that cigarette sales decrease is due to after-tax price?

My reasons: If consumers were aware of the tax increase, they would have bought more cigarette packs before such increase (this is a very reasonable assumption just as assuming health risks to be a cause of declining sales for choice B).

Logic: Aware beforehand so consumers buy more --> After increase consumers do not buy or buy at a normal rate --> hence the 'comparitive' decrease.

Is my argument anywhere close to sensible thinking?

---

Ron的解释：
this doesn't work. in general, the statements "if X happens, then Y will happen" and "if X doesn't happen, then Y won't happen" are unrelated to each other.

for instance,
if i win the lottery, then i will be very happy
--> according to your logic, this would mean that i will actually be unhappy if i don'twin the lottery.
i think you see the problem here.

---

我考虑C的原因和上边那段说的一样，请牛牛解释一下。
另外，对于Ron的这个解释不懂，我理解的是，Ron说，aware税收会提高导致提高前多买，不证明不知道税收会提高，提高前就不会多买了。但是排除它因不就是这个原理么？把可能造成这个结果的其他原因排除？就像B，information改变会改变购买量，于是就说information不改变。请牛牛解释，谢谢

cician

补充，又想了想，是不是这个most的问题？因为不是all,所以没法作用？
顺便顶一下，请牛牛指教

cician

顶一顶，路过讨论下～～～

irenetopia

额，逻辑小白路过……
你的疑问在哪里呢，木有看懂
RON的意思是
如果购买者知道税会上升，他们会在上升前大量购买
和
如果购买者不知道税会上升，他们就不会在上升前大量购买烟
这两个不相关

irenetopia

C的话最多只能解释烟的购买量上升和before tax increase相关
不能解释烟的购买量下降和after相关啊

cician

irenetopia 发表于 2013-11-15 23:15
C的话最多只能解释烟的购买量上升和before tax increase相关
不能解释烟的购买量下降和after相关啊 ...

谢谢回复，疑问如下
Doesn't choice C also eliminate a potential cause to the effect that cigarette sales decrease is due to after-tax price?

My reasons: If consumers were aware of the tax increase, they would have bought more cigarette packs before such increase (this is a very reasonable assumption just as assuming health risks to be a cause of declining sales for choice B).

Logic: Aware beforehand so consumers buy more --> After increase consumers do not buy or buy at a normal rate --> hence the 'comparitive' decrease.

Is my argument anywhere close to sensible thinking?

irenetopia

cician 发表于 2013-11-16 18:22
谢谢回复，疑问如下
Doesn't choice C also eliminate a potential cause to the effect that cigarette  ...

这么想
问题问的是销售量的上升和烟税价格密切相关
问加强

你的C中，消费者没有意识到烟税会上升如果加上前提“烟税上升后销量下降了”
那么这个意思就是，由于消费者意识影响了烟的销量

其实在一定程度上，是削弱了题目，因为C一旦成立，原题结论“烟的销量和烟税密切相关”就不成立了，因为其实是消费者意识在影响烟的销量懂不？

B为什么正确呢，我们把B取非，如果消费者的健康意识改变，那么烟的销量就是被健康意识影响的，结论被削弱，但是B说没有变化，也就是否定了第三因素，从反面加强选项

cician

irenetopia 发表于 2013-11-16 18:49
这么想
问题问的是销售量的上升和烟税价格密切相关
问加强

消费者意识到税后价格会上升，所以才提前多买，还是税后价格影响的呀？

irenetopia

cician 发表于 2013-11-16 20:48
消费者意识到税后价格会上升，所以才提前多买，还是税后价格影响的呀？ ...

按这个思路了，税后影响的就应该是第三因素，消费者意识，然后消费者意识影响到销量
所以就不是税和销量的直接关系了，属于削弱

cician

irenetopia 发表于 2013-11-16 21:03
按这个思路了，税后影响的就应该是第三因素，消费者意识，然后消费者意识影响到销量
所以就不是税和销量 ...

明白你的意思啦，谢谢
对于Ron说的 A＝》B不能说明非A＝》非B，你怎么想的呢？这个说法虽然有道理，但是平时我们做逻辑题驳斥的时候不是经常这么处理么？这个B选项不明显，我去锁模一道题，再举个例子。。。