Self-study
Bicycle safety expert: Conclusion Bicycling on the left half of the road is much more likely to lead to collisions with automobiles than is bicycling on the right. █████ ████ ██ █████ █████████ ███████ ██ ██████████████████ ███████████ ███ █████████ ███ ██████ ██ ███ ████ ██ ███ ███ ███ ██ ███████ ██ ███ ██████ █████████████
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Objective: Identify a Flaw
The question stem asks us to find a flaw in the bicycle safety expert's argument, and because the expert speaks first, this means that we can ignore the skeptic altogether. It's possible the skeptic could point out something useful in the expert's argument, but in principle, we will likely be able to answer this question just based on the expert's argument.
So what is that argument? The expert concludes that biking on the left is more likely to lead to bike-car collisions compared to biking on the right. In support, the expert cites 3 studies, which found that bike-car collisions involved cyclists biking on the left in 15 to 25 percent of cases. But hang on a minute—these numbers don't have any context, so they don't mean much. If very few cyclists bike on the left, then those percentages are really large. But if most cyclists bike on the left, then the studies would actually suggest it's pretty safe to do so.
This is why the question stem says the strength of the expert's argument "cannot be evaluated": because without context, we can't tell if the studies support the conclusion. We need to find the answer choice that reflects this, and calls out the expert for giving collision numbers without telling us the context of how many cyclists bike on the left.
21.
One reason the strength of ███ ███████ ██████ ██████████ ████████ ██████ ██ █████████ ██ ████
a
the statistics cited ██ ███████ ██ ███ ██████████ ████ █████████ ██ ███ ████ ██ ████ ██████ ██ ████ ██ ██████████ ████ ███████████ ███████ ██████████ ███ █████ ██ ████ ██████████
(A) describes circular reasoning, but that's not what the expert does. The expert's statistics aren't very useful, but they don't rest on the assumption that biking on the left is more dangerous.
b
the statistics it █████ ██ ███ ███████ ███ ██████████ ██ █████████ ████ ████ █████ ██ ███ ████
This is the missing context that we would need to evaluate the expert's argument. Without knowing how many cyclists actually bike on the left, we can't say whether the collision rates cited are high or low, so we can't judge how (un)safe left-side biking really is.
c
no statistics are ████████ ██ ███ ██████████ ██ ███████ █████████ ████ ███ ███ ██ ██████████████████ ██████████
The expert's argument is already limited to bike-car collisions, so this information wouldn't make any difference. Knowing about other types of bike accidents wouldn't help us evaluate if left-side biking is more likely to lead to a bike-car collision.
d
bicycling on the ████ ██ ███████ ███ ███ █████████ ███████ █████████████ ██ █████ █████████ █████████ ████ ███ ██████
The (un)safety of other practices wouldn't make a difference to the (un)safety of left-side biking. That information doesn't prevent us from evaluating whether biking on the left is really more likely to lead to bike-car collisions, as the expert claims.
e
it does not ███████████ ███████ ██████ ██ █████ █████████ ██ ███ ████ ██ █████ ███ ██████ ██ █████ ██ ██ ███████
The expert is talking about biking on the left in general, so whether it's legal doesn't matter. Legality doesn't make any difference to evaluating the safety of left-side biking.