[求助]T-9-Q4

shallowshade

1.       T-9-Q4.

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.

每包香烟的税增加8分的哪一年，销售量下滑10％。

在增税之前的那一年，销售量下滑了1％。

à
香烟的销售量和每包香烟的税后价格高度相关。

（基本假设：增加的这8分，会让今年的税后价格较去年高）

The argument above requires which of the following assumptions?

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.
（前一年的税前价格增加较多，今年的税前价格增加较少，则不知增加8分的税后价格是增加还是减少，因此不能做成本论之结论）
The one percent fall in cigarette sales in the year prior to tax increases was due to a smaller tax increase.（支持结论，而非结论之基本假设）
The pretax price of a pack of cigarettes gradually decreased throughout the year before and the year after the tax increase.（税前价格逐年降低，则不知税后的价格是增加还是减少，因此不能做成本论之结论）
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.（如果在增加8分之前的税前价格就比原来的税前价格低了八分或更低，则即使增税八分，税后价格还是比较低，所以要排除这个就是这个因果关系的基本假设）
As the after-tax price of a pack of cigarettes rises, the pretax price also rises.（税后价格增加，税前价格也同时增加，无法确定这个增加是由税所引起的，还是由原本的价格所引起的，所以无法确定税收影响销售额之因果关系。）

-- by 会员 newjoshkao (2009/7/24 16:21:00)

由此楼看明白的，税后价格=税前价格+税，题目的结论是税后价格与香烟的销量高度相关，也就是说今年销量下降的比去年多，说明今年税后价格比去年高，但是这里由于不知道两年的税前价格，所以这种推测是缺少假设的，如果说今年的税前价格不会比去年的税前价格低超过8cent，那么加上这8cent之后，推测就成立了，否则今年的税后价格仍然比去年低，就不可能出现销量下降更多的情况。个人觉得11楼少说了一点，这里应该是两年间税前和税后价格的比较