GMAT逻辑统计枚举推理特征比较明显,从理论上讲解比较简单,但是在解题过程中其突破点却不易被发现。需要我们在练习中时刻警惕,练出应对这类题的敏锐视角。
1、定义:枚举归纳推理是由所见的某一类事物的部分分子具有某种属性,而且没有遇到相反的情况,于是得出这一类事务都是具有这种属性的一般性结论。枚举归纳推理的结论是或然的,它的可靠程度是和事例数量相关的。
2、特点:前提的范畴将会在结论中被扩大,简单来说就是由样本推总体。比如,我们在上海卢湾区做了一项调查,发现有 90%的人患有病 A,结论就是在整个上海市也有 90%的人患有病 A。
3、形式:Premise:A中有N%是B。Conclusion:A+C中有N%是B)。
1、统计枚举推理的解题要点:只要是统计枚举模式的推理,答案选择中必须出现“样本”,就是抽象形式中的A。
2、GMAT逻辑其实考的是评估论证,类比推理也不例外,而评估论证的方法称为 Critical Question,简称CQ。评估的方向有四种,有问加强,有问削弱,这里我们用削弱来举例统计枚举推理的CQ模式。
CQ1:样本是否具有代表性?是不是用来推理的样本是特殊的?加强就说这个样本具有代表性,削弱就说这个样本不具有代表性,或者具有特殊性。
CQ2:样本的数量是否足够?削弱的话,可以举另一个例子D中并不是有N%的是B。
1、数字不等于比例。比如说给出一个比例是增长10,但是我们不知道基数是多少,所以我们没有办法比较增长的是多是少,即使可能这个比例是比去年同期要高的。反过来给了数字说比例也是犯得同样错误。
2、单独不等于相对。比如说我们的人均收入增长了每人一万,这样看来是挺高的了。可是我们要与其他的临近国家做对比,如果临近国家的人居收入每人增加了十万,那我们的一万也就不算什么了。
3、平均值不等于每一个。每一个平均值的背后都隐藏着时间和空间上的不平均。比如说全国人民的收入平均上涨,但是实际上是会有人下降的。比如说是一年的上涨,完全就有可能1-10月份上涨,11-12月份是下降的。
4、分子不等于分母。不光要看到分子,也要看到分母的逆向变化。比如说一个城市的犯罪率是1/5000,某一天分子变成了10,人们很恐慌,但事实上分母增长到了60019,犯罪率还降低了。
5、样本不等于总体。如果不告诉我们抽样办法,不告诉我们总体规模的话,样本很难代表整体。
6、时间。如果一个调查研究的结果不告诉我们调查的时间的话,有可能时间就比较久远,那它的可信度就很低。
Often patients with ankle fractures that are stable, and thus do not require surgery, are given follow-up x-rays because their orthopedists are concerned about possibly having misjudged the stability of the fracture. When a number of follow-up x-rays were reviewed, however, all the fractures that had initially been judged stable were found to have healed correctly. Therefore, it is a waste of money to order follow-up x-rays of ankle fracture initially judged stable.
Which of the following, if true, most strengthens the argument?
A. Doctors who are general practitioners rather than orthopedists are less likely than orthopedists to judge the stability of an ankle fracture correctly.(全科医生的判断没有骨科医生那么准确,但并没有提到样本 a number of follow-up x-rays,所以既不是加强也不是削弱)
B. Many ankle injuries for which an initial x-ray is ordered are revealed by the x-ray not to involve any fracture of the ankle.
C. X-rays of patients of many different orthopedists working in several hospitals were reviewed. (只有这个选项是有 a number of follow-up x-rays,说的是不同的医生看的,显然是唯一的答案。)
D. The healing of ankle fractures that have been surgically repaired is always checked by means of a follow-up x-ray.
E. Orthopedists routinely order follow-up x-rays for fractures of bone other than ankle bones.
统计枚举推理分析:
通读原文,找到结论句:Therefore, it is a waste of money to order follow-up x-rays of ankle fracture initially judged stable.
看前提:When a number of follow-up x-rays were reviewed, however, all the fractures that had initially been judged stable were found to have healed correctly.
逻辑链(前提和结论之间的推理关系):因为reviewed的样本a number of follow-up x-rays是 have healed correctly,所以结论说it is a waste of money to order follow-up x-rays of ankle fracture initially judged stable,意思就是所有的 x-rays 都应该是 have healed correctly。
看问题:问题让我们加强,那么就是说这个样本是具有代表性的,可以推而广之。
找选项:提到这个样本的代表性的。
GMAT逻辑解题原则前程百利小编为大家简单介绍这些,遵循逻辑解题的客观性原则是前提也是基础,在客观的基础上利用技巧去高效地排除错误选项是逻辑解题的关键,希望大家能够重视。
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