请教LSAT-3-I-22,23

joywzy · 发表于 2003-5-12 22:49:00

22. In an experiment, two-year-old boys and their fathers made pie dough together using rolling pins and other utensils. Each father-son pair used a rolling pin that was distinctively different from those used by the other, "father-son pairs, and each father repeated the phrase "rolling pin" each time his son used it. But when the children were asked to identify all of the rolling pins among a group of kitchen utensils that included several rolling pins, each child picked only the one that he had used.

Which one of the following inferences is most supported by the information above?
(A) the children did not grasp the function of rolling pin.

(B) No two children understood the name "rolling pin" to apply to the same object

(C) The children understood that all rolling pins have the same general shape.

(D) Each child was able to identify correctly only the utensils that he had used.

(E) The children were not able to distinguish the rolling pins they used from other rolling pins.

答案：B，这是怎么来的啊要？

23. When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast. of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use. the vast majority of those who test positive will be people who have used cocaine.

A reasoning error in the argument is that the argument

(A) attempts to infer a value judgment from purely factual premises.

(B) attributes to every member of the population the properties of the average member of the population.

(C) fails to take into account what proportion of the population have used cocaine.

(D) ignores the fact that some cocaine users do not test positive.

(E) advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine.

答案：C，我一见数学题，人就晕，就搞不明白这些数字是怎么来的怎么去的。

谢谢。

mindfree · 发表于 2003-5-12 23:05:00

1. 此题可以理解成conclusion题型. 答案可以用排除法找到.

A. 错. 原文没有提到是否掌握rolling pin的功能, 他们不挑出其它的pin也不能说明是因为未掌握功能, 可能是其它原因.
B. 对.
C. 错. 与原文的现象相反, 如果知道就不会只找出自己用过的.
D. 错. 这是解释想象的原因之一, 而不是结论, 由只找自己用的rolling pin推广到所有的utensil不对.
E. 与原文相反

2. 这类题目在ETS中很常见, 前几天的一道关于oxygen-18的题目很类似, 此题中有两种人A和B, 结论是5%的A小于99%的B. 这里忽略了A和B的基数. 如果A远远大于B(或A>(99/5)B), 原不等式就不成立. 这种题目应该是迷惑美国人的, 你在阅读是要很快找到问题.

cranberry · 发表于 2003-5-12 23:13:00

1, 文中给定的前提是，孩子用擀面杖（姑且这样叫），都是擀面杖，但模样不同，最后从工具里挑擀面杖时，只会挑出自己用过的那一个。可以推出，对孩子来讲，擀面杖这个词只是代表他用过的那一个而已。

joywzy · 发表于 2003-5-12 23:20:00

1，其它好排除。就是D不是跟原文说的一样吗：

原文： each child picked only the one that he had used.

D：Each child was able to identify correctly only the utensils that he had used.

为什么D错？

joywzy · 发表于 2003-5-12 23:26:00

以下是引用mindfree在2003-5-12 23:05:00的发言：

2. 这类题目在ETS中很常见, 前几天的一道关于oxygen-18的题目很类似, 此题中有两种人A和B, 结论是5%的A小于99%的B. 这里忽略了A和B的基数. 如果A远远大于B(或A>(99/5)B), 原不等式就不成立. 这种题目应该是迷惑美国人的, 你在阅读是要很快找到问题.

Thus, when a randomly chosen group of people is tested for cocaine use. the vast majority of those who test positive will be people who have used cocaine.

===>结论是5%的A小于99%的B. ？？？？

mindfree,能再讲讲吗？谢谢。

mindfree · 发表于 2003-5-13 00:04:00

原文说5%的不用coke的人会被误测, 而99%的用coke的人会被测出来.所以在一个sample人群中测coke, 被测出positive的人中大多数是用coke的人. 这里可以看出来positive的人包括5%不用coke而被误测的人加上99%用coke的人. 结论是99%用coke的人要多于5%不用coke的人. 这里的错误是我们只知道两个百分比, 没有绝对的数值, 而且两个百分比的基数不同, 无法比较. 如果不用coke的人有一万个, 用的有一百个, 那么positive的人有10000*5%+100*99%=599.般其中误测的就多于正确的.

cranberry · 发表于 2003-5-13 00:13:00

以下是引用joywzy在2003-5-12 23:20:00的发言：
1，其它好排除。就是D不是跟原文说的一样吗：

原文： each child picked only the one that he had used.

D：Each child was able to identify correctly only the utensils that he had used.

为什么D错？

D说的不准确，文中只说了擀面杖可没说别的工具

joywzy · 发表于 2003-5-13 06:44:00

明白了，谢谢mindfree ,cranberry!!!

问题还是出在阅读上啊。数学题那题，我就是没读出结论来5%A<99%B。

[此贴子已经被作者于2003-5-13 6:46:44编辑过]

请教LSAT-3-I-22,23

请教LSAT-3-I-22,23

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