Motor-scooter dealers attribute a drastic decline in sales over the

Motor-scooter dealers attribute a drastic decline in sales over the last few years to a new law requiring motor-scooter riders to wear helmets. Previously, helmets had been obligatory for motorcycle riders but not for motor-scooter riders-a difference that the dealers argue made scooters preferable for many customers. Safety advocates, however, dispute the dealers' explanation, pointing out that the law's introduction coincided with a large increase in the cost of mandatory insurance for both types of vehicle.

In evaluating the safety advocates' and the dealers' explanations, it would be most helpful to know which of the following?

Information that helps with evaluating an explanation will support or cast doubt on that explanation. So, we're looking for the choice that names information that would support or cast doubt on the explanations, and since we have two different explanations, the information will probably support one while casting doubt on the other.

A. Whether there were any motor-scooter riders who regularly wore helmets before the law required them to do so

Knowing this would not help with evaluating the argument.

After all, regardless of whether there were "any" motor-scooter riders who regularly wore helmets before the law required them to do so, the law could still have affected most motor-scooter riders, who went from not having to wear helmets if they rode motor-scooters to having to wear helmets.

In other words, "any motor-scooter riders" could be a tiny percentage of motor-scooter riders, in which case, the helmet law would still have made a difference to the vast majority of motor-scooter riders.

Eliminate.

B. Whether the cost of mandatory insurance for other motor vehicles has increased at the same rate as the insurance cost for motor scooters and motorcycles

Notice that this choice mentions "the same rate." "The same rate" is just one specific thing, a rate that is the same.

Having information on whether the cost increased at "the same rate" wouldn't help.

After all, if the cost of insurance for other motor vehicles has increased at the same rate as that for motor scooters and motorcycles, then it still could be the case that people became less inclined to buy motor scooters because of either the helmet law or the increase in the insurance rate. Maybe people just didn't feel like spending the money, or maybe they didn't want to wear helmets.

Alternatively, if the cost of insurance for other motor vehicles has not increased at the same rate, we have no idea about what happened with that cost. Did it increase? Decrease? Remain the same? We don't know.

So, this information either makes no difference or has unclear implications.

Eliminate.

C. How the accident rate for motor scooters compares to the accident rate for motorcycles

Knowing this would not help with evaluating the argument. Here's why.

Presumably, the accident rates for motor scooters and motorcycles would have remained about the same over time, or at least haven't suddenly changed "drastically." So, how the two rates compare has likely remained about the same over time as well.

Something that remains about the same would not explain or cause a new change such as a "drastic decline." In fact, it's useful for CR to keep in mind that, in general, something that remains the same will not be the cause of a new change.

So, knowing how the accident rate for motor scooters compares to the accident rate for motorcycles would not help in evaluating the argument since that comparison would not be an alternative cause for the "drastic decline in sales over the last few years."

Thus, regardless of how the two accident rates compare, that information would not be reason to believe or not believe the safety advocates' and the dealers' explanations.

Eliminate.

D. How sales of imported motor scooters have changed compared with sales of domestically produced models

Regardless of how sales of imported motor scooters have changed compared with sales of domestically produced models, it's still the case that, after the helmet law came into existence and insurance rates increased, overall sales of motor scooters declined. So, having the information mentioned by this choice would not really change what we know about the scenario.

Eliminate.

E. How sales of motorcycles that are close in purchase price to motor scooters have changed over the period that scooter sales have declined

Having this information would help us to evaluate the argument. Here's how.

Motorcycles that are close in purchase price to motor scooters are products similar to motor scooters.

Also, we know from the passage that insurance rates have increased for both motor cycles and motor scooters.

On the other hand, the helmet law change applies to motor scooters only.

Let's consider some ways sales of motorcycles that are close in purchase price to motor scooters could have changed.

Increased - In this case, sales of motor scooters have declined while sales of similarly priced motorcycles have increased. That information would tend to confirm that the helmet law made the difference since the increase in insurance rates didn't cause the sales of motorcycles to decline.

Remained the same - In this case, we have a situation similar to the one in which sales of motorcycles increased. Sales of motor scooters have declined while sales of similarly priced motorcycles have remained the same. That information would tend to confirm that the helmet law made the difference since the increase in insurance rates didn't cause the sales of motorcycles to decline.

Decreased - In this case, sales of motorcycles have declined just as sales of scooters have. That information would support the conclusion that the increase in insurance cost caused the decline in motor-scooter sales since both motor-scooter sales and also motorcycle sales declined at the same time, the change in insurance costs affected them both, and the helmet law affected only motor scooters.

We can see that having this information helps us to determine which explanation is correct.

The correct answer is (E).