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 More drivers and front-seat passengers in the survey than reat-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.
A): A why? [CXD: p254, 30]作者: StephanieYun 时间: 2003-7-27 11:22
这是一道数学比例的题目。选项成立时题目的结论才会成立。
题目的结论是: 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. , 题目给出的条件是: among the severely injured drivers and front-seat passengers , more than 80% were not wearing seat belts at the time of their accidents. 要有这个条件就说明结论的成立显然有缺陷。 选项正是补充这个deficiency. while at the same time, from the point of view of demonstration, the question belongs to the kind of rate-question. That is , by comparing two rates , which are depicting the severeness of two groups among the survey, the author could logically infer that by wearing seat belts, drivers and front seat passengers could greatly reduce their risk of being severely injured. What is said in choice A would be the one rate which is compared to the one in the argument.
