A recent report determined that although only 3 percent of drivers on

Well, if the conclusion is mentioned in the question itself, then I guess we should start by making sure we're 100% clear about the language in the conclusion:

"...drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not."

Great. And since this is a runty little two-sentence passage, the evidence to support the conclusion is pretty straightforward:

"...although only 3 percent of drivers on Maryland highways equipped their vehicles with radar detectors, 33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them."

A few details of language jump out at me in this passage, though. For starters, the conclusion emphasizes that drivers who equip their vehicles with radar detectors are more likely to actually exceed the speed limit regularly than drivers who do not. And it's interesting to me that the evidence focuses on the percentage of ticketed vehicles that were equipped with radar detectors.

So if we're looking for an assumption, then we probably will need something that connects the conclusion (i.e., that drivers with radar detectors actually exceed the speed limit regularly) with the evidence about speeding tickets. And as always, you can think of an assumption as something that not only strengthens or reinforces the conclusion, but also is necessary to draw that conclusion.


(A) strengthens the conclusion: if drivers with the radar detectors are LESS likely to be ticketed than drivers without them, then the drivers with radar detectors must exceed the speed limit even MORE often than it initially seemed based on the argument.

Trouble is, the question isn't asking us to strengthen the argument; it's asking us to identify a necessary assumption. And we don't need to assume that drivers with radar detectors are less likely to be ticketed than other drivers. After all, 33% of ticketed vehicles have radar detectors, while only 3% of all vehicles have radar detectors, so if vehicles with radar detectors are just equally likely to receive tickets when they exceed the speed limit, the conclusion could still hold. Heck, drivers with radar detectors could even be somewhat more likely to receive tickets -- and as long as the disparity isn't huge, the conclusion could still hold.

So we certainly don't need to assume that vehicles with radars are LESS likely to receive tickets. (A) is out.


This answer choice seems so lame and obvious -- of course you're more likely to exceed the speed limit if you receive more speeding tickets, right? -- that I kind of want to ignore it completely. But that would be a bad thing to do.

Let's come back to the argument: the conclusion says that people with radar detectors ACTUALLY exceed the speed limit more often than drivers without them, but the evidence in the passage only mentions the fact that vehicles with radar detectors receive a disproportionate percentage of TICKETS for speeding. So we absolutely do need to assume that drivers who receive tickets are more likely to actually exceed the speed limit. Otherwise, there's no connection whatsoever between the evidence and the conclusion.

So let's keep (B).


There's no reason why we would need to assume this in order to draw the conclusion. We already know that 3% of drivers equipped their vehicles with radar detectors, and it doesn't really matter whether 6% of all vehicles or 2% of all vehicles receive speeding tickets: either way, it wouldn't change the fact (stated in the passage!) that vehicles with radar detectors receive a disproportionate percentage of those tickets. And more importantly, it wouldn't help us figure out whether drivers with radar detectors are more likely to actually exceed the speed limit.

So (C) is gone.


(D) is kind of interesting, but it doesn't actually help us draw the conclusion.

For starters, we don't know which vehicles were ticketed more than once: if the vehicles with radar detectors were more likely to receive multiple tickets, then it would reinforce the idea that vehicles with radar detectors receive TONS of tickets. But it could also go in the other direction: if vehicles WITHOUT radar detectors were more likely to receive multiple tickets, then it would weaken the force of the evidence in the passage, and undermine the conclusion. For that reason alone, we could ditch (D).

And just as importantly: remember that the conclusion discusses the likelihood that drivers actually exceed the speed limit. (D) doesn't help us reinforce this conclusion at all, because it just tells us something about the number of tickets received for speeding.

So we can eliminate (D), too.


Who gives a crap? The entire scope of the passage is about drivers in Maryland, and the conclusion is concerned with differences in behavior between drivers with and without radar detectors in Maryland. Comparing Maryland drivers to non-Maryland drivers can't possibly have any impact whatsoever on the conclusion.

So we can eliminate (E), and (B) is the best answer.