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billytang1980 发表于 2005-4-26 09:37 ![]()
14. A recent survey of all auto accident victims in Dole County found that, of the sever ...
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.
因为如果样本中的戴安全带的人少于20%，那么文中的80%就不具有说服力了
|
| Injury without seat belts
| Injury with seat belts
| Total with
| Total without
| 80
| 20
| 800
| 200
| 1:10
| 1:10
| 900
| 100
| 8:90
| 2:10
| 500
| 500
| 8:50
| 2:50
|
用黄色标记的，说明更加安全。所以当总人数中，使用安全带的人数少于20%的时候，结论不成立
(B) Considerably more than 20 percent of drivers and front-seat passengers in Dole County always wear seat belts when traveling by car.
跟他们的习惯无关，不在调查范围之内
(C) More drivers and front-seat passengers in the survey than rear-seat passengers were very severely injured.
无关比较
(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.
“一半”无法证实80%的有效性（A）
(E) Most of the auto accidents reported to police in Dole County do not involve any serious injury.
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发表于 2011-7-1 15:38:08
