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

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A recent report determined that although only three percent of drivers  [#permalink]

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A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?


(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.

(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.

(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.

(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.


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Originally posted by stolyar on 01 Jul 2003, 07:02.
Last edited by Bunuel on 10 Oct 2018, 21:49, edited 1 time in total.
Renamed the topic and edited the question.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 14 Aug 2010, 12:55
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Hey All,

I can explain that difference! Let's take this from the top.

A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

Conclusion: Driver with radar exceed the speed limit more than those with no radar.
Premise: 3% of drivers have radar. 33% of ticketed vehicles have them.
Assumption: Something else about the radar doesn't make you more likely to get ticketed. Speed = tickets.

The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
PROBLEM: This is the opposite of what we want. The people with radar are clearly getting tickets MORE often than those who do not.

(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
ANSWER: This is dangerous, because most people ASSUME this already (if you get tickets more, it's because you're speeding more). But remember this is the GMAT, we cannot assume this. We can't jump from "more tickets" to "more speeding", as much as our logic nodes may want it.

(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
PROBLEM: We don't need to assume this to make our conclusion. Try negating it, and seeing if that destroys the conclusion (this is a way to test correct assumptions). "The number of vehicles that were ticketed for exceeding the speed limit was NOT greater than the number of vehicles that were equipped with radar detectors." So what? It could still be true that people with radar are speeding more.

(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
PROBLEM: Even if this might work, it's the OPPOSITE of what we'd want. We'd want to assume that these people were only ticketed ONCE, because if the same person was ticketed multiple times, he might only be one person, in which case the conclusion doesn't work. But the negation of this is: "Many of the vehicles that were ticketed for exceeding the speed limit were NOT ticketed more than once in the time period covered by the report." That HELPS the argument, see? Now we can possibly infer that there are MORE PEOPLE with radar speeding, because there are no duplicates.

(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.
PROBLEM: Who cares about stuff outside of Maryland?

Hope that helps!

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Re: A recent report determined that although only 3 percent of drivers on  [#permalink]

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New post 23 Jan 2018, 23:44
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Quote:
A recent report determined that 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. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?

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.

Quote:
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.

(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.

Quote:
(B) Drivers who are ticketed for exceeding speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

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).

Quote:
(C) The number of vehicles that were ticketed for exceeding speed limit was greater than the number of vehicles that were equipped with the radar detectors.

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.

Quote:
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.

(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.

Quote:
(E) Drivers on Maryland highways exceed the speed limit more often than drivers on other state highways not covered in the report.

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.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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Only a tiny fraction of people have the radar detectors. However, one-third of tickets go to people with radar detectors.

Radar detectors are associated with increased incidence of tickets.

But how do we know that those getting caught are speeding regularly?

You don't, unless you assume it (B).

Very tricky because of all the verbiage.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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saurya_s wrote:
171. A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not. The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.


B must be the answer. The argument cites high incidence of radar-equipped cars BEING TICKETED but derives a conclusion about how often these cars EXCEEDED THE SPEED LIMIT. Clearly, in the author's opinion those drivers who are often ticketed often exceed the speed limit. Thus, B is the missing link
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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3% of drivers on maryland highways equip their vehicles with radar detectors
31% of all vehicles ticketed for exceeding the speed limit were equip with them
Drivers who equip their vehicles with radar detectors are more likely to exceed speed lmiit regularly than driver who do not <-- conclusion

(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
- does not hold up the conclusion

(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
This one holds up the conclusion. We're told a large percentage of vehicles with radar detectors were ticketed for speeding. Then (B) says those who are ticketed are likely to exceed the speed limit regularly. So the conclusion that vehicles with radar detectors exceed the speed limit regularly is true.

(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
- not important.

(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
- does not help the conclusion

(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.
- out of scope
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 13 Dec 2008, 17:36
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I've seen this one before, and I believe it is an LSAT question. The answer is B. It works like this:

Conclusion: Drivers who have radar detectors are more likely to exceed the speed limit regularly than drivers who do not.

Evidence: 3% of drivers on Maryland highways had radar detectors in their vehicles, but 33% of vehicles which got speeding tickets on Maryland highways had radar detectors.

What does the evidence prove? If 3% of the vehicles have radar detectors but those vehicles account for 33% of the tickets, then the evidence DOES prove that vehicles with radar detectors are more likely to get a ticket. Their share of the total number of tickets is greater than their share of the total number of vehicles. This makes it arithmetically inevitable that the percentage of them (again, this is the detector-equipped cars) which gets tickets is bigger than the percentage of other cars which gets tickets.

The conclusion, however, does NOT say that the vehicles with radar detectors are more likely to get a ticket. It says that they are more likely to exceed the speed limit REGULARLY. So the missing assumption is that a vehicle or driver which gets a ticket is therefore also more likely to exceed the speed limit REGULARLY. The evidence proves that these vehicles get more tickets; we need the missing assumption (choice B) to go from there to the conclusion.

The wording of the question actually allows for another, much more subtle flaw in the argument -- one which is NOT used in these answer choices. The evidence actually doesn't say that 3% of VEHICLES have radar detectors; it says that 3% of DRIVERS equip their vehicles with radar detectors. Because of this, the argument also depends on assuming that this 3% of drivers do NOT collectively own 33% or more of the vehicles on Maryland highways. If they did, then it would be possible for the proportion of all vehicles with radar detectors to be the same as, or higher than, the proportion of all tickets which go to those vehicles.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 24 Nov 2010, 20:54
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goalsnr wrote:
A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.
The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.


Let's look at the question stem first. We need to find an assumption. An assumption is a missing necessary premise. Something that will not only strengthen the conclusion but also be essential to the argument.
An assumption is a statement that needs to be added to the premises for the conclusion to be true.

Premises:
- Only 3% of drivers on Maryland highways had radar detectors.
- 33% of vehicles that got speeding tickets had radar detectors.

Conclusion: Drivers with radar detectors are more likely to exceed the speed limit regularly than other drivers.

There must be a disconnect between the premises and conclusion since there is an assumption. Look carefully. Premises give a connection between radar detectors and vehicles that get speeding tickets. While conclusion concludes a relation between radar detectors and vehicles that exceed speed limit. The assumption must then give a connection between vehicles that get speeding tickets and vehicles that exceed speed limit.
Option (B) gives us that relation.

Lets add it to premises and see if the conclusion makes more sense now:

- Only 3% of drivers on Maryland highways had radar detectors.
- 33% of vehicles that got speeding tickets had radar detectors. (links radar detector to speeding tickets)
-Drivers who get speeding tickets are more likely to exceed the speed limit regularly than others. (links speeding tickets to exceed speed limit)

Conclusion: Drivers with radar detectors are more likely to exceed the speed limit regularly than other drivers. (links radar detectors to exceed speed limit) Perfect!

Option (C) only tells us that people without radar detectors were also ticketed. It doesn't strengthen our conclusion at all.
Option (D) tells us that many vehicles were ticketed multiple times. It doesn't say that these vehicles had radar and had been over speeding regularly. Hence option (D) isn't the missing premise either.
You can also apply the Assumption Negation Technique here. If you negate (B) conclusion cannot be drawn.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 25 Nov 2010, 14:13
sheru34766 wrote:
Thanks Karishma. That was helpful.

But geesh, :shock: , would I be able to put all these together in 2mins?


In most CR questions, you will need to break down the stimulus into premises and conclusion. If your question is asking for assumption, then you are looking for missing data. Then you actively search for a missing link between premises and conclusion. With some practice you can very easily and quickly narrow down your choices. Then you can use assumption negation technique in those if you are not certain. Sometimes, you could exceed 2 mins in tricky CR questions but in SC questions you should be generally be done within 1min 30 sec. So it is a good idea to practice pacing yourself using practice tests.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 07 Aug 2011, 17:36
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Guys, classic scope shift as indicated by mismatch of subject in the main assertion and the assumption choices – driver vs vehicle! The element that needs to be connected for the argument to work is the subject ‘driver’. In choice D the subject morphs into something slightly different, which seem consistent, or even inferable from the argument. Hence B.

Another form of common scope shift is when the author uses a word or concept in two different ways where the intent is to blur the main topic - equivocation. For example, ‘airplanes seats have been designed for safety’ is different from saying ‘airplanes seats are safe’.

Another common shift arises in the main conclusion itself when we find something else comes out of nowhere, in which case the job is to connect that ‘something else’ in the conclusion with something in the premise in order to make the argument work. Hence we make it focal point of assumption hunt.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 14 Mar 2012, 17:44
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It's definitely a tricky one :).

The conclusion states that drivers with radar detectors speed more REGULARLY than those who do not carry radar detectors. Notice how I highlighted the word 'regularly.'

The conclusion is based on the fact that 33% of those ticketed carry radar detectors (whereas only 3% of total drivers are ticketed). From this fact alone can we say that radar-detector drivers speed regularly? They obviously sped once - they got a ticket. But there is no way we can say that they speed regularly. So this is an assumption that the argument rests on, the assumption addressed in (B):

(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

Hence the answer is (B).
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 28 May 2012, 03:22
VeritasPrepKarishma wrote:
goalsnr wrote:
A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.
The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.


Let's look at the question stem first. We need to find an assumption. An assumption is a missing necessary premise. Something that will not only strengthen the conclusion but also be essential to the argument.
An assumption is a statement that needs to be added to the premises for the conclusion to be true.

Premises:
- Only 3% of drivers on Maryland highways had radar detectors.
- 33% of vehicles that got speeding tickets had radar detectors.

Conclusion: Drivers with radar detectors are more likely to exceed the speed limit regularly than other drivers.

There must be a disconnect between the premises and conclusion since there is an assumption. Look carefully. Premises give a connection between radar detectors and vehicles that get speeding tickets. While conclusion concludes a relation between radar detectors and vehicles that exceed speed limit. The assumption must then give a connection between vehicles that get speeding tickets and vehicles that exceed speed limit.
Option (B) gives us that relation.

Lets add it to premises and see if the conclusion makes more sense now:

- Only 3% of drivers on Maryland highways had radar detectors.
- 33% of vehicles that got speeding tickets had radar detectors. (links radar detector to speeding tickets)
-Drivers who get speeding tickets are more likely to exceed the speed limit regularly than others. (links speeding tickets to exceed speed limit)

Conclusion: Drivers with radar detectors are more likely to exceed the speed limit regularly than other drivers. (links radar detectors to exceed speed limit) Perfect!

Option (C) only tells us that people without radar detectors were also ticketed. It doesn't strengthen our conclusion at all.
Option (D) tells us that many vehicles were ticketed multiple times. It doesn't say that these vehicles had radar and had been over speeding regularly. Hence option (D) isn't the missing premise either.
You can also apply the Assumption Negation Technique here. If you negate (B) conclusion cannot be drawn.


karishma, I understand the logic, but I think there is a HUGE detail that is being overlooked. Every forum i looked no one addresses this...

if 33% of the people ticketed have radar detectors, then 67% of those ticketed DO NOT. Therefore, with B, those 67% ticketed and without radars are also more likely to speed regularly than those who are not ticketed. But wait a second, now it seems we're supporting something counter to the conclusion.

So now this becomes a percentages problem because the only way B is a proper assumption for the conclusion is if the percentage of people with radars is very small, hence the reason the problem uses 3%. If it was 34%, for instance, i think we can argue that B does not work.

** the reason I mention this is because in addition to myself, i notice a lot of people getting hung up on the percentages and the "paradox" that results from it. and then most people, including the OG explanation, don't bother mentioning the percentages, which I think are absolutely crucial.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 28 May 2012, 03:58
pinchharmonic wrote:
karishma, I understand the logic, but I think there is a HUGE detail that is being overlooked. Every forum i looked no one addresses this...

if 33% of the people ticketed have radar detectors, then 67% of those ticketed DO NOT. Therefore, with B, those 67% ticketed and without radars are also more likely to speed regularly than those who are not ticketed. But wait a second, now it seems we're supporting something counter to the conclusion.

So now this becomes a percentages problem because the only way B is a proper assumption for the conclusion is if the percentage of people with radars is very small, hence the reason the problem uses 3%. If it was 34%, for instance, i think we can argue that B does not work.

** the reason I mention this is because in addition to myself, i notice a lot of people getting hung up on the percentages and the "paradox" that results from it. and then most people, including the OG explanation, don't bother mentioning the percentages, which I think are absolutely crucial.


Of course it is a percentages problem. The reason no one mentions it is because it is obvious. The whole argument is based on the chosen numbers. "ALTHOUGH ONLY 3% of drivers on Maryland highways equipped their vehicles with radar detectors, 33% of all vehicles ticketed for exceeding the speed limit were equipped with them."
- A very small number has radar detectors BUT they represent a big part of offenders who are caught. This makes you conclude something and you need to point out the assumption.

If you change the numbers (put 33% in place of 3%), the argument falls apart and ceases to make any sense. 33% have radar detectors and 33% of offenders who are caught have radar - that's balanced representation so you cant conclude anything from that.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 13 Nov 2012, 12:17
A recent report determined that 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.
Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the spped limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions:

1. Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
2. Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
3. The number of vehicles that were ticketed for exceeding the spped limit was greater than the number of vehicles that were equipped with radar detectors.
4. Many of the vehicles that were ticketed for exceeding the spped limit were ticketed more than once in the time period covered by the report.
5. Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.


Hello Experts,

I'm having difficulty understanding the question (Question # 77), in the OG 13.

Choice (2) is mentioned as the correct answer.
Not sure how this is the correct choice.

I can eliminate options 1 and 5 right away, as Opposite effect and OFS respectively. The rest are difficult to eliminate.
The answer choices provided look more like inference, than like assumptions


Thanks,

Abhijit
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 13 Nov 2012, 19:55
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abhichar wrote:
Hello Experts,

I'm having difficulty understanding the following question (Question # 77), in the OG 13.

A recent report determined that 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.
Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the spped limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions:

1. Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
2. Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
3. The number of vehicles that were ticketed for exceeding the spped limit was greater than the number of vehicles that were equipped with radar detectors.
4. Many of the vehicles that were ticketed for exceeding the spped limit were ticketed more than once in the time period covered by the report.
5. Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.



Choice (2) is mentioned as the correct answer.
Not sure how this is the correct choice.

I can eliminate options 1 and 5 right away, as Opposite effect and OFS respectively. The rest are difficult to eliminate.
The answer choices provided look more like inference, than like assumptions


Thanks,

Abhijit


The standard eGMAT approach is fairly straight forward: You have to first read the passage and identify the conclusion and the premises. The next step is to pre-think, when you try to find the gap between the path from the premises to the conclusion. This gap is what is filled by the assumption.

Let's first identify the conclusion and the premises:
Conclusion: drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.
Premise: 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 --->> In other words, 3% of vehicles with radar detectors account for 33% of vehicles ticketed for exceeding speed limit and the rest 97% that don't have radar detectors account for 67% of tickets.

Now, comes the pre-thinking stage:

On the basis of just the premise, we can conclude that drivers with X (vehicles fitted with radar detectors) are more likely to be ticketed than drivers without X.

However, the conclusion states that drivers with X are more likely to exceed the speed limit regularly than are drivers without X.

So, this conclusion talks about:
1. "more likelihood of exceeding the speed limit" rather than just "more likelihood of getting ticketed"
2. It also adds "regularly" to the condition exceeding the speed limit.

Let's for the time being ignore "regularly" word here. What assumption is required to come from our conclusion (which was derived just on the basis of the premise) to the given conclusion.

The assumption is that drivers who are ticketed for over-speeding are the ones who are over-speeding. (This is what should ideally be the case)

However, the given conclusion also has "regularly" adjective. Thus, an assumption is required which links the people that get ticketed to the ones who over-speed regularly. We can see from the options that only option 2 does this and thus, is the correct choice.

However, for the sake of completion, let's also consider options 3 & 4 also:

3. The number of vehicles that were ticketed for exceeding the spped limit was greater than the number of vehicles that were equipped with radar detectors. - This means that there at least some vehicles that are fitted with radar detectors, which were ticketed more than once. However with this assumption, we can't say:
a) that the vehicles that get ticketed exceed the speed limit (the ideal case assumption is not stated here)
b) and that they exceed the speed limit regularly (regularly means a recurring phenomena, not just a thing which has occurred more than once)

4. Many of the vehicles that were ticketed for exceeding the spped limit were ticketed more than once in the time period covered by the report - Again the same logic as in 3rd option.

I hope it helps. If you have any further queries, please feel free to ask.

Regards,
CJ
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 18 Feb 2013, 10:07
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sagarsingh wrote:
abhichar wrote:
[color=#0000ff]A recent report determined that 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.
Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the spped limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions:


Everything written above makes sense, I just want to focus on the main takeaway of this question as this issue comes up over and over again in Critical Reasoning. The question sets you up with drivers who get ticketed, and then a conclusion is made for all drivers who exceed the speed limit regularly. The GMAT frequently makes these kinds of leaps in logic, and the answer is always the choice that reconciles the group given in the premise (ticketed for speeding) with the group extrapolated for in the conclusion (regularly exceeds the speed limit).

Once you learn how to spot these questions, either through clear conceptual understanding or myriad similar examples, these are easy breezy questions. And if you can get a few easy questions on the exam, then you have more time for the head scratchers.

Hope this helps!
-Ron
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 19 Feb 2013, 08:46
Hi thangvietnam,

there are multiple examples that have a similar takeaway to the question above. Allow me to post the illustrative example we use during the Veritas course on Critical Reasoning:

Dr. Larson: Sleep deprivation is the cause of many social ills, ranging from irritability to potentially dangerous instances of impaired decision making. Most people today suffer from sleep deprivation to some degree. therefore we should restructure the workday to allow people flexibility in scheduling their work hours.

Which of the following, if true, would most strengthen the medical doctor's argument?

(A) The primary cause of sleep deprivation is overwork.
(B) Employees would get more sleep if they had greater latitude in scheduling their work hours.
(C) Individuals vary widely in the amount of sleep they require.
(D) More people would suffer from sleep deprivation today than did in the past if the average number of hours worked per week had not decreased.
(E) The extent of one's sleep deprivation is proportional to the length of one's workday.

I'll let people post their thoughts, but this is a typical question where the premise is about a certain group of people and the conclusion seems to be about a somewhat different different group of people. Using the lesson learned in the "speeding" question above, the correct answer here should reconcile this gap.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 06 Mar 2013, 12:03
The stimulus says that although drivers who equipped their cars with the radar detectors were a minority (only 3%), they accounted for a significantly higher proportion (33%) for vehicles ticketed for exceeding the speed limit. The stimulus then concludes that this means that drivers who equip their cars with the radar detectors are more likely to regularly exceed the speed limit than drivers who do not fit their cars with radar detectors.

What can be the assumptions underlying this argument? Lets look at the answer choices.
(A): If the drivers with radar detectors in their cars are less likely to be ticketed, how does this help us conclude that they will more regularly exceed the speed limit? Just because they are less likely to be caught does not mean they will regularly flout the speed limit.
(B): This sounds right. The stimulus assumes that drivers ticketed for exceeding the speed limit are likely to do it regularly. Think about it. If this is not true, then the conclusion that drivers with radar detectors are more likely to regularly exceed the speed limit than drivers who do not fit their cars with radar detectors falls apart.
(C): This is unverifiable and does not help us reach the conclusion in any way. The conclusion is not dependent on the number of vehicles.
(D): If this is true, then it is possible that a small number of errant drivers with radar detectors in their cars are exceeding the speed limit and getting caught again and again. This might mean that a majority of drivers with the detectors in their cars are actually driving within speed limits, which makes the conclusion fall apart.
(E): If this is true, it again weakens the conclusion. This might mean that the results of the Maryland highway ticketing do not hold elsewhere. Therefore it is possible that drivers with radar detectors on other highways are in fact more responsible, and also less. We just don't know. Therefore this does not strengthen the conclusion in any way.

B is therefore the correct answer.
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 24 Apr 2013, 16:03
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FACT 1:
A recent report determined that although only 3 percent of drivers on Maryland highways equipped their vehicles
with radar detectors,
FACT 2:
33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them.
CONCLUSION:
Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly
than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?

Even though a few vehicles have radars, 33% of the ticketed had it. The conclusion, as often happens in the GMAT when we have numerical data, assumes the validity of the data itself: uniformity, no distortions, ...
So before reading the answers we have to keep this in mind: the data must be "true", must represent the reality.
Movin on to the answers, we now can see why B is correct.

(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly
than are drivers who are not ticketed.

With B we know that the data does represent the reality, and the conclusion is not based on few cases. If you want with assumption cases you can negate the option and see if the argument holds.
If you do so you obtain "Drivers who ... are less likely to"; here it's easier to see that the conclusion (without B) is based on unreliable data.

Hope this helps, let me know
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Re: A recent report determined that although only three percent of drivers  [#permalink]

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New post 07 Aug 2013, 15:48
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We'll attack this question with some framework + prethinking.

Framework: Expectation vs Actuality
Pre-thinking: Link the two relevant topics

This question starts off with the expectation vs actuality framework
Expectation: 3% (low percentage) with radar detectors ->might expect 3% of ticketed cars to have radar detectors
Actuality: 3% (low percentage) with radar detectors -> actually 33% of ticketed cars have radar detectors

Conclusion: Those using radar detectors are MORE likely to exceed speed limit REGULARLY.

Keep in mind that the word "regularly" adds a dimension of "degree" into the conclusion. It's not a simple relationship between "detector = speed more", but rather "detector = consistently speed more"


So our pre-thinking should be to find an answer choice that connects those two topics:
1) something to do with "detector"
2) something to do with "consistently speeding more" -- keyword 'consistently' is important

(B) [Drivers who are ticketed for exceeding the speed limit ] are [ more likely to exceed the speed limit regularly]
than are drivers who are not ticketed.


So does (B) talk about the detector? Not directly BUT it does so indirectly.
[Drivers who are ticketed for exceeding the speed limit ]
We already established before that a good percentage of those who are ticketed (33%) are those WITH detectors. Thus (B) is already referencing this segment of the population. Then the second half says this group (those with detectors) are more likely to exceed the speed limit REGULARLY -- fully captures the conclusion we had. In fact, it almost sounds like a repeat of the conclusion -- but it does so by substituting that first part ("detectors") with something slightly different.



(A) [ Drivers who equip their vehicles with radar detectors ] are [less likely to be ticketed for exceeding the speed
limit ]
than are drivers who do not.

1) "detector" -- YES
2) "consistently speeding more" -- NO, goes in opposite direction and says LESS likely.



(C) [ The number of vehicles that were ticketed for exceeding the speed limit ] was greater than the number of
vehicles that were equipped with radar detectors.
1) "detector" -- no, this is talking about the # of vehicles...not the population of those that speeded. Notice the other answer choices reference "drivers" -- not "the number of vehicles"
2) "consistently speeding more" -- no


(D) [ Many of the vehicles that were ticketed for exceeding the speed limit ] were ticketed more than once in the
time period covered by the report.
1) "detector" -- no, this is talking about some detail about a portion of the vehicles -- we only care about the drivers that used the "detector" -- not the details about some irrelevant segment
2) "consistently speeding more" -- no

(E) [ Drivers on Maryland highways ] exceeded the speed limit more often than did drivers on other state
highways not covered in the report.

1) "detector"-- no, talks about drivers in Maryland as a whole. The conclusion only cares about drivers who used the detector, not the whole group.
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Re: A recent report determined that although only three percent of drivers   [#permalink] 07 Aug 2013, 15:48

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