标题: 求教高手，如何提高逻辑水平？ [打印本页] 作者: 木川 时间: 2003-8-5 02:32 标题: 求教高手，如何提高逻辑水平？ 我现在巨郁闷！！！ 做了第七套LSAT题，有一题如下： 10. A large group of hyperactive children whose regular diets included food containing large amounts of additives was observed by researchers trained to assess the presence or absence of behavior problems. The children were ten placed on a low-additive diet for several weeks, after which they were observed again. Originally nearly 60 percent of the children exhibited behavior problems; after the change in diet, only 30 percent did so. On the basis of these data, it can be concluded that food additives can contribute to behavior problems in hyperactive children.
The evidence cited fails to establish the conclusion because
(A) there is no evidence that the reduction in behavior problems was proportionate to the reduction in food-additive intake
(B) there is no way to know what changes would have occurred without the change of diet, since only children who changed to a low-additive diet were studied
(C) exactly how many children exhibited behavior problems after the change in diet cannot be determined, since the size of the group studied is not precisely given
(D) there is no evidence that the behavior of some of the children was unaffected by additives
(E) the evidence is consistent with the claim that some children exhibit more frequent behavior problems after being on the low-additive diet than they had exhibited when first observed 我开始选的答案是C，因为我觉得给出了比率，文中没有出现具体的人数，所以试验本身值得置疑。 随后发现不对，因为我实际犯了一个大错误，就是又开始置疑前提事实，而不是去反对结果。然后我又重新看，发现B选项和E 选项似乎都正确。然后我查看了新东方费费讲的逻辑，觉得这应该是逻辑题中的第三类型，就是用B推出A否。而E选项正是相同的前提得出了一个不同的结论。反对了A。 可是看答案，发现是B。虽然似乎也能够想的通，可是如果选B，不正和我刚刚选C的情形一样么？置疑了前提啊！！！ 我晕点了我，请高手指点。
