Bicycle Safety expert : Bicycling on the left half of the road is much more likely to lead to collisions with automobiles than is bicycling on the right . After all , in three different studies of bicycle-automobile collisions , the bicyclist was riding on the left in 15,17 and 25 percent of the cases respectively .

Skeptic : But in places where a comparatively high percentage of bicyclists used to ride on the left , there was suprisingly little decrease in collisions between bicyclists and automobiles after bicycling on the left was made illegal .

One reason the strength of the bicycle safety expert's argument cannot be evaluated is that

(A) The statistics cited in support of the conclusion is that bicycling on the left is more likely to lead to collisions with automobiles already pressupose the truth of the conclusion

(B) The statistics it cites do not include the percentage of bicycling that took place on the left

(C) No statistics are provided on the proportion of bicycle accidents that are due to bicycle automobile collisions .

(D) Bicycling on the left is singled out for criticism without consideration of the other bicycling practices that are unsafe

(E) It does not distinguish between places in which bicycling on the left is legal and places in which it is illegal .

I'm completely lost on this questions , could you guys help me out ? I haven't understood the stimulus itself properly .

Original Answer - B
Please give me explanations and not just your answer . This is from the Veritas Prep CR Book .

The stimulus is basically asking "what is wrong with the argument?" This is at the heart of most CR questions. See what you can do with this and then let us know if you get stuck later in the problem..

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Tim Sanders
Manhattan GMAT Instructor

How do you decide it's asking what is wrong in the argument?

It says that bicycling on left is much more likely to cause collision and presents the statistics. It gives the percentage of cases in which collision happened on left-side ride i.e. 15% and so on. Now, we don't know the percentage of times there was a left-side ride with and without collisions. This would be what would be required to evaluate whether collision is most likely on the left side.

Look at the question: "One reason the strength of the bicycle safety expert's argument cannot be evaluated is that"

If I am unable to evaluate the argument, then something substantial that is part of the argument must be incorrect or missing. This would mean that the argument is not perfectly solid and thus has a flaw.

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Jamie Nelson
ManhattanGMAT Instructor