问一道逻辑题（陈向东的逻辑推理）

minivicki

这道题是陈向东编的GMAT逻辑推理 书中的，因为找不到有关这本书中题目的讨论，所以新开一贴，麻烦nn们帮忙解释下。

P503 

10. A recent survey showed that 50 percent of people polled believe that elected officials should resign if indicted for a crime, whereas 35 percent believe that elected officials should resign only if they are convicted of  a crime. Therefore, more people believe that elected officials should resign if indicted than believe that they should resign if convicted.

The reasoning above is flawed because it

A. draws a conclusion about the population in general based only o a sample of that population

B. confuses a sufficient condition with a required condition

C. is based on an ambiguity of one of its terms

D. draws a conclusion about a specific belief based on responses to queries about two different specific beliefs

E. contains permises that cannot all be true

答案是b, 我选了a

实在想不通b所谓的充分条件，必要条件是怎么对应文中的推理？

minivicki

怎么没人回复阿？

是不是这本书里面的题目没有意义啊？

NN们请指教一下吧。

12345678lj

帮顶，看不出B项和题目的关系。莫非，题目错了？

luweihaororo

indicted for a crime（被起诉）是be convicted a crime（被定罪）的必要条件。一定是先被起诉，再被定罪。所以原文有问题。前提是35%认为官员应该辞职ONLY IF他们被定罪，到了结论ONLY IF没了，那么，认为被定罪该辞职的人，就应该是50％＋35％＝85％，因为认为起诉就该辞职的人，当然认为被定罪的该辞职。那么，实际结论应该与原文结论相反。

所以，原文混淆了充分与必要条件，将indicted与convicted两者的推导顺序弄反了，才会得出那样的结果。

minivicki

谢谢楼上阿。

一下子明白了。

ccc1983

显然50%和35%的比较基数没有说明。如果基础一样则能得出结论。显然文中说明的只是一个必要条件，基数相同是另一个必要条件；文中直接得出结论犯了这样的错误，把必要条件当成是充分条件。

yizihuishi

因为PREMISE部分是recent study，但是结论是普遍性的，所以一般不可以推特殊