PTF97.S3.Q21 Bicycle safety expert

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  Claudia77 Member

  August 2022 106 karma

  Safety expert: Biking on the left side of the road rather than the right side is much more likely to lead to collisions with cars. According to three different studies, the cyclist was riding on the left side in 15-25% of collisions.

  The question stem asks us to provide a reason as to why the strength of the expert's claim cannot be evaluated.

  Answer choice A states that the statistics cited in support of the expert's conclusion presuppose the truth of that conclusion. The expert's conclusion is that "biking on the left side of the road is more likely to lead to a collision than biking on the right." However, the statistics cited don't assume that that is true. The studies mentioned each examined a series of collisions and found that in 15-25% of collisions the cyclist was biking on the left side of the road. Obtaining this result does not require the expert's conclusion to be true.

  Answer choice B states that the statistics cited by the expert do not include the percentage of cycling that took place on the left. This answer identifies a problem with the expert's argument: the expert said that the cyclist was riding on the left in 15-25% of car-bicycle collisions, but they didn't say how often people bike on the left side of the road. If, say, 90% of cyclists bike on the left-side, then the studies indicate that the left side is actually relatively safe (and render the expert's argument weak). However, if only 10% of cyclists bike on the left, that means that 15-25% of collisions involve only 10% of cyclists, which would indicate that the left side is in fact dangerous. Hence, until we know how much biking on the left-side of the road occurs, we can't evaluate the strength of the expert's argument.