Lawyer-Assumption 条件型结论（充分必要）的理解，求指导！

冰雪蜂鸟 · 发表于 2011-5-28 19:46:35

5．ASSUMPTION
看原文：同WEAKEN。对于充分必要的，列出推理链。

找答案：答案分两类型：SUPPORT（填补推理上的概念GAP），DEFENDER（排除WEAKEN结论的可能性，即排除他因）。读原文，推理中有概念GAP（特别是答案出现新元素），则答案填补这个GAP（通常新元素必出现），否则找他因，排除推理中的WEAKNESS。最后用TEST检验或排除易混的答案。对于后一类用有关无关有时比较好，用结论的具体性和特殊性去分有关无关，排出剩下的用TEST

DENIAL TEST：将选项取非，原文结论不成立，则为正确选项。

几种特殊类型：

因果型结论：ASSUMPTION的方法包括：A。不是其他原因或可能导致该结果。B。结合因果：或有因有果或无果无因。C。因果没颠倒。D显示因果关系的资料是准确。

条件型结论：结论带条件（即为充分必要）。ASSUMPTION的方法排除充分条件出现，必要条件不出现的情况。或充分条件一定能推出必要条件，或排除充分条件推不出必要条件的可能

原文是类比：ASSUMPTION方式为两者本质不是不同

调查：肯定有效性（被调查的对象有代表性等）
==================================================================================

之前还看到过一个帖子说：美国人思维不讲求充分性，只讲求必要性。不一定这样做了一定会达到某种效果，但提供一种可能。

==================================================================================

我的问题：哪位好心人可以帮忙解释一下什么是充分性，必要性，什么样的选项可以作为答案？可能是高中数学没有太理解逻辑这块，还烦请各位好心人可以拿一道你们理解得比较好的题做一下示范~ 我觉得干看充分性必要性这些讲解和说法，太难以理解了。拜谢~

MarsTOF · 发表于 2011-5-28 23:10:20

假设 A是条件 B是结论
AB能互推证明A是B的充要条件
A能推出B B不能反着推出A A是B的充分非必要
A不能推出B B能推出A A是B的必要非充分。。

冰雪蜂鸟 · 发表于 2011-5-28 23:32:42

谢谢好心的Mars！我拿一道题来！

112. The average hourly wage of television assemblers in Vernland has long been significantly lower than that in neighboring Borodia. Since Borodia dropped all tariffs on Vernlandian televisions three years ago, the number of televisions sold annually in Borodia has not changed. However, recent statistics show a drop in the number of television assemblers in Borodia. Therefore, updated trade statistics will probably indicate that the number of televisions Borodia imports annually from Vernland has increased.

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

(A) The number of television assemblers in Vernland has increased by at least as much as the number of television assemblers in Borodia has decreased.
(B) Televisions assembled in Vernland have features that televisions assembled in Borodia do not have.
(C) The average number of hours it takes a Borodian television assembler to assemble a television has not decreased significantly during the past three years.
(D) The number of televisions assembled annually in Vernland has increased signifi cantly during the past three years.
(E) The difference between the hourly wage of television assemblers in Vernland and the hourly wage of television assemblers in Borodia is likely to decrease in the next few years.

答案：C

OG上的解释：That piece of evidence is relevant only as an indication that the number of TVs being produced within Borodia has decreased. But a drop in the number of TV assemblers does not indicate a drop in the number of TVs being assembled if the number of TVs an average assembler puts together has increased.

我感觉这道题应该属于Lawyer说的条件型（如果不是一定要指出啊！），答案是C没有问题。只分析逻辑过程的话，哪一个是充分条件，哪一个是必要条件呢？如何推理呢？
如果这个不是典型的条件型，还麻烦帮忙拿一道题呢，我真的是很麻烦，抱歉了！谢谢！

sdcar2010 · 发表于 2011-5-29 02:29:16

Premise: Televisions are made in both V and B, and B imports TV from V. The number of televisions sold in B keeps constant. These TV's come from both B and V. The number of TV assemblers in B decreases.

Conclusion: TV imports from V to B has increased.

The assumption is that if TV assemblers in B are fewer, there will be fewer TV made in B. A further assumption is that the efficiency of TV assemblers in B has not changed (answer C).

If you use negation method, you would find that after negating C, the argument falls apart. If assemblers in B become more efficient, they can produce the same amount or more TV than before, even with a lower number of total assemblers.

sdcar2010 · 发表于 2011-5-29 02:30:39

Be simple.

If A, then B. A is the sufficient condition for B to happen and B is the necessary conditon when A is present.

冰雪蜂鸟 · 发表于 2011-5-29 09:08:53

谢谢sdcar2010，但是对不起我还有一点疑问。

If A, then B. 中的A，B是一般出现在什么位置呢？是在文章中出现，A为Premise,B为Conclusion？还是A为Conclusion,B为一个能够推出A的选项？
我感觉应该是第二种，像这道题的话，A为Conclusion：TV imports from V to B has increased. 那么添加一个能够使A成立的必要条件就可以了！B：没有变的更有效率。B使A成为可能。
如果是这样的话，其他任何能够使A成为可能的必要条件都有机会成为正确选项，比如：The price of TV assembled in B has increased.
而选项不能为A的充分不必要条件的原因就是，选项没有稳固A的成立。

不知道我这个想法对不对啊，如果不对还要麻烦一定要狠狠的指出啊！！！

那么这道题的话A,B无关，E为无关的时间，D的话我感觉有点关系，如何排除呢？还请指点！！！

sdcar2010 · 发表于 2011-5-29 13:07:39

If A, then B.
A is the premise and B is the conclusion. A is the sufficient condition and B is the necessary condition.

冰雪蜂鸟 · 发表于 2011-5-29 22:25:29

If A, then B.
A is the premise and B is the conclusion. A is the sufficient condition and B is the necessary condition.

-- by 会员 sdcar2010 (2011/5/29 13:07:39)

如果这样的话，A和B不就构成一个完整的逻辑了吗？也就不需要填补GAP了呀？

sdcar2010 · 发表于 2011-5-29 23:15:11

Premise: Televisions are made in both V and B, and B imports TV from V. The number of televisions sold in B keeps constant. These TV's come from both B and V. The number of TV assemblers in B decreases.

Conclusion: TV imports from V to B has increased.

The assumption is that if TV assemblers in B are fewer, there will be fewer TV made in B. A further assumption is that the efficiency of TV assemblers in B has not changed (answer C).

In terms of formal logic the argument is the following:
If 1) TV's sold in B come from both B and V; and 2) the number of TV assemblers in B decreases, then 3) TV imports from V to B has increased.

Both 1) and 2) are the premises of the argument. 3) is the conclulsion of the argument.

P.S.
"If A, then B" or A-->B is a simplified expression of every logic statement. But an argument might be consisted of several such logic statements: If A then B. If B then C. Therefore, if A then D. Here the assumption is if C then D.
In other words, a premise of an argument might contain several logic statements. So might the conclusion of the argument. One should not confuse the premise for each logic statement with the premise for the argument.

If the conclusion says if A then B, there might be gaps to connect A with B in that argument since A might be a chain of logic statement which lacks one of its logic links.

sdcar2010 · 发表于 2011-5-29 23:31:08

谢谢sdcar2010，但是对不起我还有一点疑问。

If A, then B. 中的A，B是一般出现在什么位置呢？是在文章中出现，A为Premise,B为Conclusion？还是A为Conclusion,B为一个能够推出A的选项？
我感觉应该是第二种，像这道题的话，A为Conclusion：TV imports from V to B has increased. 那么添加一个能够使A成立的必要条件就可以了！B：没有变的更有效率。B使A成为可能。
如果是这样的话，其他任何能够使A成为可能的必要条件都有机会成为正确选项，比如：The price of TV assembled in B has increased.
而选项不能为A的充分不必要条件的原因就是，选项没有稳固A的成立。

不知道我这个想法对不对啊，如果不对还要麻烦一定要狠狠的指出啊！！！

那么这道题的话A,B无关，E为无关的时间，D的话我感觉有点关系，如何排除呢？还请指点！！！

-- by 会员冰雪蜂鸟 (2011/5/29 9:08:53)

A conlusion in any argument is a necessary condition for the sufficient condition of the same argument.

A necessary assumption for an argument is a must-be-true condition for the conclusion of the same argument to occur. In that sense, LZ's statement "If conclusion (A), then necessary assumption (B)" is absolutely right! However, this is not the same as "If necessary assumption (B), then conclusion (A)" or "B使A成为可能." The correct way is If NOT necessary condition, then NOT conclusion, which is the logic behind the negation method!

LZ, you need to read LR Bible to get a clear picture of what premise vs. conclusion, necessary condition vs. sufficient condition, logic statement vs. argument are all about. Learn more about formal logic. It would help you to simplify logic reasoning questions and to find the correct answers thereto in shorter time.

Lawyer-Assumption 条件型结论（充分必要）的理解，求指导！

所属分类: GMAT考试

正在浏览此版块的会员 ()