GWD 13 Q4 大家都来看看你能做对么？

bluesolo

In the years 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 cigarette sales is therefore strongly related to the after-tax price of a pack of cigarettes.

The argument above requires which of the following assumptions?

A.During the year following the tax increase, the pretax price of a pack of cigarettes did not increase by as much as it had during the year prior to the tax increase.

B.The one percent fall in cigarette sales in the year prior to tax increases was due to a smaller tax increase.

C.The pretax price of a pack of cigarettes gradually decreased throughout the year before and the year after the tax increase.

D.For the year following the tax increase, the pretax price of a pack of cigarettes was not eight or more cents lower than it had been the previous year.

E.As the after-tax price of a pack of cigarettes rises, the pretax price also rises.

这道题我想的不是很明白：
逻辑链为：
tax涨8分钱，sales掉10%，而前一年sales掉1%。结论：销量和涨价后的价格是强相关的。

我选的B，因为我觉得如果sales和价格正相关，则去年tax涨少于8分钱，所以销量-1%，小于10%，所以tax和sales减少成正比。
但是答案为D。谁能帮忙解释一下，谢谢!

teddybearj4

这道题用取非就可以了。题目中有一个这样的formula：after-tax price = tax + pretax price

conclusion是sales跟after-tax price 有反比关系，也就是after-tax price上涨，sales下降。题目说了tax上涨了8 cents。取非D，pretax price是比以前降低了8cents or more，这样formula的右边就比以前要小。那就变成after-tax price下降，sales下降，正比关系了，weaken了原conclusion。

bobdog159

楼主，注意不是涨价后的价格，是税收提高以后的税后价格。 如果税收提高了8分钱，而税前价格降低了8分钱（D选项的情况）那么其实税后价格（after-tax price）是没有变的，所以 sales和after-tax的相关关系就不存在了。即D选项一定不能成立。

bobdog159

打错了，D一定要成立。。。

tthere

这道题用取非就可以了。题目中有一个这样的formula：after-tax price = tax + pretax price

conclusion是sales跟after-tax price 有反比关系，也就是after-tax price上涨，sales下降。题目说了tax上涨了8 cents。取非D，pretax price是比以前降低了8cents or more，这样formula的右边就比以前要小。那就变成after-tax price下降，sales下降，正比关系了，weaken了原conclusion。

-- by 会员 teddybearj4 (2012/4/15 17:10:57)

为什么会有这样一个formula呢

ink989

这道题用取非就可以了。题目中有一个这样的formula：after-tax price = tax + pretax price

conclusion是sales跟after-tax price 有反比关系，也就是after-tax price上涨，sales下降。题目说了tax上涨了8 cents。取非D，pretax price是比以前降低了8cents or more，这样formula的右边就比以前要小。那就变成after-tax price下降，sales下降，正比关系了，weaken了原conclusion。

-- by 会员 teddybearj4 (2012/4/15 17:10:57)

感觉cr能够提取题干很重要！

zuozuo923

新人冒个泡，我对此题的思路，化成公式是这样的：

设：烟销量为X，收税时期为A，不收税时期为B。

A  导致 X  下跌10%
B  导致 X  下跌1%   由这两项推出结论：X与税后价格有关（此结论包含了作者的假设：A,B两时期，税后价格的差异只是这8分）

故：D选项说税前价格没有降低8分或更多，保证了作者的假设成立。 D 为正确答案