The growing popularity of computer-based activities was widely expected to result in a decline in television viewing, since it had been assumed that people lack sufficient free time to maintain current television-viewing levels while spending increasing amounts of free time on the computer. That assumption, however, is evidently false: in a recent mail survey concerning media use, a very large majority of respondents who report increasing time spent per week using computer report no change in time spent watching television.

Which of the following would be most useful to determine in order to evaluate the argument?

A.      Whether a large majority of the survey respondents reported watching television regularly

B.       Whether the amount of time spent watching television is declining among people who report that they rarely or never use computers

C.      Whether the type of television programs a person watches tends to changes as the amount of time spent per week using computer increases

D.      Whether a large majority of the computer owners in the survey reported spending increasing amounts of time per week using computers

E.       Whether the survey respondents’ reports of time spent using computers included time spent using computers at work.

答案选E，不过我选了A。想请教一下A为什么是无关项。

我是这样理解的，A的意思为：需要确定大部分的respondents中是否都经常看电视。也就是说，如果这些人不是经常看电视的，比如一天只看5分钟电视，那么他们回答称，看电视的时间不变的话，其实这个样本就不是很有意义了。

即：对A选项，否定回答，削弱了样本的代表性，也就削弱的结论。

                        肯定回答，增强了样本的代表性，起加强作用。

如楼主所说, 如果A选项真的是怀疑样本有效性, 那么, 则有可能成为答案, 但是A不是,

两种方法解答:

1. 无关排除, (建议实战或者, 模考时使用)

文中说的是一般人, 没有说是常看电视的人, A说人是否是常看电视的人, 与题目无关, 排除

2. 分析(建议平时练习时使用)

文中说:

1. computer上升 导致 空余时间减少, 而空余时间减少 导致 TV 下降

2. 报告显示: computer上升, TV不变

结论, 条件1错

如何评价呢?

E说, 是否computer上升包括在公司用computer工作

如果是, 则C上升不导致,空余时间减少, 则不能说条件1为假, 则削弱结论

如果否, 则C上升导致空余时间减少, 但是空余时间减少不导致TV下降, 则加强结论

 
A说, 被调查者是否经常看电视

如果是, C上升导致空余时间减少, 但是空余时间减少不导致TV下降, 则加强结论

如果否, C上升导致空余时间减少, 但是空余时间减少不导致TV下降, 还是加强结论

因此不是答案

楼主说, 不经常看电视,如只看5分钟 则样本无意义,

但是事实是, 文章说, 只要C上升, 则TV下降, 哪怕原来只看5分钟, 也必然下降, 变成4分钟, 3分钟, 2

分钟....

所以样本是有意义的

"如果是, 则C上升不导致,空余时间减少, 则不能说条件1为假, 则削弱结论"——此提法有误！！！

应该是：“如果是, 则C上升不导致空余时间减少, 削弱条件1, 则削弱结论”。