大全Test2-14

panbangzhu

14. A recent survey of all auto accident victims in Dole County found that, of the severely injured drivers and front-seat passengers, 80 percent were not wearing seat belts at the time of their accidents. This indicates that, by wearing seat belts, drivers and front-seat passengers can greatly reduce their risk of being severely injured if they are in an auto accident.
The conclusion above is not properly drawn unless which of the following is true?
(A) Of all the drivers and front-seat passengers in the survey, more than 20 percent were wearing seat belts at the time of their accidents.
(B) Considerably more than 20 percent of drivers and front-seat passengers in Dole County always wear seat belts when traveling by car.
C(C) More drivers and front-seat passengers in the survey than rear-seat passengers were very severely injured.
(D) More than half of the drivers and front-seat passengers in the survey were not wearing seat belts at the time of their accidents.
(E) Most of the auto accidents reported to police in Dole County do not involve any serious injury.

答案选A，但是我不知道A选项和原题中的evidence如何indicate得出这个结论，evidence说的事情似乎和A差不多啊，一个是80% were not wearing，另一个是more than 20% were wearing？
谢谢NN们解答哈！

87338618

注意题干和A中的差别
题干说：受重伤的人中系安全带的/所有受重伤的人=20%  (severely injured)
A说：受伤的人中系安全带/所有受伤的人 > 20%
不过，我想了半天，也说不清楚为什么A对。
帮你顶一下~

panbangzhu

谢谢LS的回答，期待更多人讨论!!

lovesiqi4665

原文中说80%受重伤的人没带安全带
但是假如带安全的人本来就很少，在少到一定程度之后，带安全带的安全系数可能还不如不带安全带
比如，假设一般来说100人中就有80人没安全带，20人有安全带，那么80%不带安全带的人受伤就是正常，所以80%就是这个临界值，只要不带安全带的人少于80%，也就是带安全带的人多于20%，那么不带安全带就是更危险，就是A啦
呵呵，不知道有没有把我想的说明白

Kminami

原文的推理过程如下， 80%的重伤者不带安全带=〉带安全带减少重伤可能（通俗点就是带了比较安全），那么这个推理是有缺陷的，题目就是让我们补上这个缺陷。那么这个缺陷是什么？试想，如果在事故中受轻伤的人也不带安全带，那么是不是就不能推出原文结论了？那么答案必然是要说明，受轻伤的人是要带安全带的。接下来，因为在受重伤的人中已经有20%的人带了安全带了，那么再加上那些带了安全带受轻伤的人，所以总的受伤人数中必有超过20%的人带了安全带。 （至此推理结束，需要说明的是最后一句话的数学原理，(N+x)/(M+x)>N/M）

hanshipeng

没看懂以上大家的解答，有人再给说说吧