大全2-14

jboy

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 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.（A）

(E) Most of the auto accidents reported to police in Dole
                County do not involve any serious injury.                       Why is not D but is A I don't find any evidence that A is correct answer...IF A is right answer why is not??please help help me...

mbz

A is right b/c if there are less than 20% of people wearing seat belts, then the fact that 80% of the people not wearing seat belt are severely injured doesn't prove the difference of wearing or not wearing a seat belt.

D is not right b/c we don't need to have more than 50% of the drivers and front-seat passengers to make the argument valid.  Remember the question:

The conclusion above is not properly drawn unless which of the following is true?

The conclusion above is not properly drawn unless which of the following is true?

jboy

I understand..but why B and C isn't right   thanks to your reply...

mbz

C is not right b/c it is irrelevant.

B is not right b/c it is just a repeatition of A, but instead makes it less valid.

Give you an example: if there are 200 students in your school, then you tell people that there are more than 199 students there. That is a good statement. However, if you say there are a lot more than 199 students, you are not wrong, but it is not as accurate at the first statement. Do that make sense?

jboy

OK..I SEE  Thanks a lot

dean703

事情是这个样的。重伤的前排人中，80%没绑安全带。所有的前排人中，有大于20%的人绑了安全带。这说明了个啥么事呢。这是想说明在坐前排的人不绑安全带是有很大几率重伤滴！因为如果绑不绑安全带没有影响的话。重伤的人没绑安全带的比例和所有的人中（都仅限前排观众）没绑安全带的比例应该是一样地，都是80%。而选项透露出的信息是所有的人中没绑安全带的比例是小于80%的，而这些没绑的小于80%的前排观众却贡献出了80%的重伤率，加强结论。