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类比推理
在GMAT逻辑的考试中，大部分题目都属于常见的条件推理（又称归纳演绎推理）方式，即通过一些条件推理得出结论。但是除了条件推理以外，逻辑里面有时也会考到其他的一些推理模型，类比推理就是其中之一。
一、类比推理的含义
用一句话总结，类比推理指的就是：基于两个对象之间的相似性，由已知对象规律推理到未知对象身上的过程。
既然是把两个对象进行类比，首先类比推理我们要分析到已知的对象和未知的对象分别是什么。而能把两个对象进行类比的前提条件就是两个对象之间的相似性。因此分析类比推理主要分析以下三个要素：
类比对象：包括已知和未知对象
类比条件：两个对象之间的相似点
类比结果：想要推理的规律以及推理是否成立
在这三要素当中国，两个类比对象之间相同还是不同是最重要的。既然类比对象之间的相似性是整个类比成立的基础，那么如果要削弱类比，就可以通过削弱相似性的方法进行；反之，如果要增强类比，就可以增强两个对象之间的相似性。
二、例题
Given that employees of the XYZ Company could, in theory, do their work at home, the company developed a radical plan to increase efficiency: eliminate office-space expenditures by having employees work at home. To evaluate this plan, XYZ’s managers asked volunteers from the company’s staff to try the arrangement for six months. There were several volunteers; significantly, their productivity during this period was as high as or higher than before.
Which of the following, if true, would argue most strongly against deciding, on the basis of the trial results, to implement the company’s plan?
(A)The employees who agreed to participate in the test of the plan were among the company’s most self-motivated and independent workers.
(B)The savings that would accrue from reduced office-space expenditures alone would be sufficient to justify implementation of the plan apart from any productivity increases.
(C)Other companies that have achieved successful results from work-at-home plans have work forces that are substantially larger than that of XYZ.
(D)The volunteers who worked at home were able to communicate with other employees as necessary for performing the work.
(E)Recent changes in the way work is organized at XYZ’s company offices have not brought about any productivity increases.
这个题目就是一个典型的类比推理，基于实验结果（trial results）想要判断这个计划实施之后的结果（implement the company’s plan）。实验证明一部分volunteer回家办公后productivity没有下降，因此就想把这个结果推广到整个公司的员工身上。类比的三个要素分析如下：
类比对象：volunteer&staff
类比条件：都是xyz员工
类比结果：productivity不下降
而这个题目是一个削弱题，需要我们去攻击类比，因此找到提出两个对象之间不同的选项：
A：volunteer是most self-motivated and independent的，通过most将volunteer和其他员工区分开，削弱两个对象之间的相似性，削弱类比。
而剩下的四个选项都没有提到两个对象之间的相似性，因此都是无关的选项，直接排除。
以上就是类比推理的分析方式及应用的技巧。
12G备考资料