HELR书上一道题绕晕求解！

cicitotheblue

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.
which of the following, if true, is the assumption that the argument above is based on?

(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 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.


正确选项是A. 上网看了各种解释还是懵懵懂懂，求高人解答，感激不尽呀！还是没明白为什么需要这个20%作为assumption

cicitotheblue

自己帮顶！

Bradz

假设在交通事故中是否系安全带与是否受到严重伤害无关，那么在样本数量足够大的情况下，参与survey的人中，总的系安全带的人的比例应该与受到严重伤害的人的比例一样，即为20%。只有当系安全带的人的比例在接受survey的总人数比例里超过20%，才能说明系安全带能够在交通事故中减少受到严重伤害的几率。

cicitotheblue

Bradz 发表于 2016-10-17 13:46
假设在交通事故中是否系安全带与是否受到严重伤害无关，那么在样本数量足够大的情况下，参与survey的人中， ...

终于懂了！真的是脑子转不过弯来了... 谢谢你！