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标题: [求助]这个答案是怎样推理的?急急的!(XDF) 39 [打印本页]

作者: icyeye    时间: 2005-2-3 01:15     标题: [求助]这个答案是怎样推理的?急急的!(XDF) 39

(XDF) 39

A recent survey of all auto accident victims in D Country found that, of the severely injured drivers and front-seat passengers, 80pct 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 20pct were wearing seat belts at the time of their accidents. (这个答案是怎样推理的?)


作者: 鹿丸    时间: 2005-2-3 15:16

只有在whole population里带安全带的人的比例高于最后出事的人中带安全带的比例时,安全带才显示出作用。当在重伤人中有20%带了,则总的样本中带了的比例要高于20%才可以有说服力




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