GMAT&LSAT-Test 2-Q14

        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.

The correct answer is A. My question is how can A support the conclusion since no information talk about the proportion of severely injured against the total surveyed?

it suddenly occured to my mind.

In other words, we can say that 20% of the severely injured were wearing seat belt at the time of their accidents, which is lower that what A states, more than 20 percent wearing seat belts of the total surveyed, who were less severely injured as a whole.

Therefore, A supports conclusion.

yes, no information, but at least the proportion is larger than 1.

That's why A is right.

This is A -> B Pattern of Assumption.