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.
(E) Most of the auto accidents reported to police in Dole County do not involve any serious injury.

Hi jitgoel,

This problem gives us evidence that 80% of injuries in car accidents are from folks not wearing seat belts. The argument's conclusion is that seat belts work. So, what's missing here? Well, we have no context about the 80%; it sounds scarily high, but we don't actually know that! The authors' assumption is that 80% of injuries makes up a disproportionate number of injuries to non-wearers. After all, if 80% of people don't wear seat belts, it's little surprise they suffered 80% of accidents! (B) tells us that this is not the case; the author's assumption that 80% is significant is in fact correct, and therefore so is his conclusion. (B) is the answer.
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Eli Meyer
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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.
(E) Most of the auto accidents reported to police in Dole County do not involve any serious injury.

Conclusion :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.

Question : which of the following has to be true to draw the above conclusion properly

It talks about auto accident not about every Cars in the city.
So Option ( B ) is ruled out in the first place.
(A) if its true then the same is going to weaken the conclusion
(C) Neither strengthening nor weakening the Conclusion
(D) ( left out ) Correct
(E) irrelevant

OA Please.

Whoops, looks like I missed something on this one!

(B) doesn't actually have to be true here. The reason is the word that should have made me suspicious from the get-go: "always." We need more than 20% of Dole County drivers to be wearing seatbelts, yes--but it doesn't have to be the same 20% on any given day. As long as more than 20% of the riders on the road are wearing their seatbelts, the argument is properly reasoned, so (B) is a (subtle) distortion.

(A), however, is the correct answer based on my reasoning above--which was the correct reasoning! Remember, the 80% that were injured is only a subset of those surveyed, the severely hurt group. We need to know that, among the group not severely injured, more than 20% were wearing seatbelts, which is what (A) gives us.

(C) is irrelevant as I said above--without relative numbers of front- and back- seat passengers, we don't know if more front- or back-seat injuries is actually an interesting result.

(D) is wrong because 49/51 and 51/49 splits of seatbelt-to-non-seatbelt-wearers are indistinguishable to us from the perspective of this article.

And, (E) is irrelevant, because in that more than half without serious injury, we don't know a thing about proportions who had seat belts.

Sorry for the confusion on the OA on this problem, and happy problem solving!
_________________

Eli Meyer
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Hi Eli,

I am still not convinced about A.

Lets say 100 people were surveyed, out of which 20 were severely injured and 80 were not severely injured.

Now, out of 20 Severely injured, 16 (80%) were NOT wearing seat belts, while 4 (20%) were wearing seat belts......Now we do not know anything about the 80 people in the survey who were NOT seriously injured .............Lets say all 80 of them were NOT wearing seat belts.

Now (A) suggests, that at the time of the accident, MORE than 20% were wearing seat belts ..........However, from the example above, we just know that only 4% (of total 100) were wearing seat belts ............so how can we know whether (A) is correct?

Please let me know if my reasoning is correct?

Thanks.