In response to mounting public concern, an airplane manufacturer implemented a program with the well-publicized goal of reducing by half the total yearly amount of hazardous waste generated by its passenger-jet division. When the program began in 1994, the division's hazardous waste output was 90 pounds per production worker; last year it was 40 pounds per production worker. Clearly, therefore, charges that the manufacturer's program has not met its goal are false.

Which of the following is an assumption on which the argument depends?


The amount of nonhazardous waste generated each year by the passenger-jet division has not increased significantly since 1994.

At least as many passenger jets were produced by the division last year as had been produced in 1994.

Since 1994, other divisions in the company have achieved reductions in hazardous waste output that are at least equal to that achieved in the passenger-jet division.

The average number of weekly hours per production worker in the passenger-jet division was not significantly greater last year than it was in 1994.

The number of production workers assigned to the passenger-jet division was not significantly less in 1994 than it was last year.

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考题讲解

情景：飞机制造商打算实施一个项目以减少整体污染排放。在这个项目开始以后，人均污染排放确实下降了。因此，这个计划达成了目的。

推理：本题中虽然有一个方案，但是最终的落脚点并不是让我们去评估这个方案的好坏，而是要我们去评估一个由人均数据推理出总体数据的推理。由于本题的前提是平均数的情况，结论是一个总体情况，所以显然是一个统计推理。

推理结构为：

前提：飞机制造商的人均污染排放下降。

结论：飞机制造商的总体污染排放下降。


选题方式：我们需要考虑平均数陷阱，即，人均是否代表总数？人数（分母）是不是增加了？

选项分析：

A选项：从1994年以来，飞机制造商客机部门排放的无危险污染并没有显著增加。

B选项：去年制造客机的数量至少和1994年制造的数量一样。

C选项：从1994年以来，其它部门排污的减少量至少和客机制造部门的一样。

D选项：去年每个员工的平均工作时间没有明显长于1994年的每个员工平均工作时间。

E选项：Correct. 1994年在客机制造部门的员工数没有明显少于去年的员工数。只有本选项谈到了人数的问题，即，所以如果工人数量发生变化，显然可以成为一个解释人均数值发生变化的因素。因此，只有本选项考虑到了平均数的陷阱。

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Prep2008E1-CR
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