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# A recent report determined that although only three percent

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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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28 May 2012, 02:22
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:

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:

-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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28 May 2012, 02:58
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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A recent report determined that although only three percent [#permalink]

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14 Aug 2012, 23:23
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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Re: A recent report determined that although only three percent [#permalink]

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15 Aug 2012, 18:00
PUNEETSCHDV 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.

A) This is exactly the revers

B) Correct. driver are ticketed more regularly than other drivers

C) Number of vehicles - who cares about vehicles we care about of drivers

D) period covered by the report - is not our problem

Hope this help
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A recent report determined that although only 3 percent of [#permalink]

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13 Nov 2012, 11:17
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: CR - OG 13 - Question No. 77 (Maryland Highway) [#permalink]

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13 Nov 2012, 18:55
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.

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 [#permalink]

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09 Feb 2013, 00:35
One technique I use in answering assumption questions is spotting a new information thrown at the conclusion. In this argument, the facts are given about ticketed for exceeding the speed limit and then a new topic pops out: exceed the speed limit REGULARLY... now that's one thing the author made an assumption about..

Premise: 33 percent of all vehicles ticketed for exceeding speed limit were equipped with radar.
Conclusion: drivers who equip their vehicles with radar are more likely to exceed speed limit REGULARY

Only B connects that: ticketed for speed limit <-> exceed speed limit regulary
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Re: A recent report determined that although only 3 percent of [#permalink]

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18 Feb 2013, 08:16
abhichar wrote:
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

Using least negation, B. If drivers who were ticketed do not get ticketed regulary, then since 33% of these had radars, there will be a situation when other people would have been ticketed who do not have radar and the conclusion will fail.

B. -- Contender and chosen as answer as explained.
C. Given in the premis: "33% of all vehicles were equipped with radar which in turn were 3 % of total vehicles.
D. Conteder 2.. rejected as it does not address about radar systems around which the conclusion is based. Also,
talks out of context.
E. Out of context.

POE would have been sufficient to answer this question.

As for OG explanation, Whenever u generalise a set which is subset of a superset,
the same generalisation must hold for the superset, which is the assumption here.
Set: radar drivers, superset: people who are ticketed.

Kudos If u like.. :D
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Re: A recent report determined that although only 3 percent of [#permalink]

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18 Feb 2013, 09:07
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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!
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Re: A recent report determined that although only 3 percent of [#permalink]

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19 Feb 2013, 07:46
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 3 percent of [#permalink]

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20 Feb 2013, 02:43
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:

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.
Opposite to conclusion
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.
vehicles with radar detectors ----> more likely to exceed the speed limit. Now , once a vehicles with radar detectors is ticketed, it is
more likely to exceed the speed limit regularly. Negation test: Suppose: Total vehicle = 100. vehicles with radar detectors = 3. If vehicles with radar detectors, once ticketed do not exceed the limit again and total tickets issued is 100 than conclusion falls apart

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.Doesn't matter
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. Doesn't matter
5. Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.OFS. we are not concerned with other state highways
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A recent report determined that although only 3 percent of [#permalink]

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06 Mar 2013, 06:51
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.

Need explanation.......why d & e is wrong & b is correct
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Re: A recent report determined that although only 3 percent of [#permalink]

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06 Mar 2013, 11:03
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 3 percent of [#permalink]

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17 Apr 2013, 04:10
imaggic wrote:
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?
(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.

OG answer is B - This is a question #78 from OG 12 CR section
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Re: A recent report determined that although only 3 percent of [#permalink]

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17 Apr 2013, 20:24
Manhatten GMAT has the OA as B with a pretty good explanation to go with it.

http://www.manhattangmat.com/forums/gmac-practice-test-critical-reasoning-t1319.html

Can we correct the answer to show B as correct and not C?
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Re: A recent report determined that although only three percent [#permalink]

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19 Apr 2013, 19:00
All duplicate threads on this topic have been merged.

Please check and follow the Guidelines for Posting in Verbal GMAT forum before posting anything.
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Highway drivers problem cant understand explain [#permalink]

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24 Apr 2013, 14:42
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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?

(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.

Last edited by Guest on 24 Apr 2013, 15:04, edited 1 time in total.
Edited the question
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Re: Highway drivers problem cant understand explain [#permalink]

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24 Apr 2013, 15:03
3
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FACT 1:
A recent report determined that although only 3 percent of drivers on Maryland highways equipped their vehicles
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: Highway drivers problem cant understand explain [#permalink]

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24 Apr 2013, 17:27
1
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Consider, There are 1000 drivers on Maryland highways.
3% i.e. 30 vehicles doesn't have radar detectors with them... (from data in CR)... (I)

Consider, 60 vehicles are ticketed for exceeding the speed limit
33% i.e. 20 vehicles didn't have the radar detectors.. (from data in CR)... (II)

From I & III,
20 vehicles with no radar detectors were out of 30 vehicles. Now consider, If 120 vehicles were ticketed, there would around 40 vehicles with no radar detectors.
Data seems to be inconsistent.

If (I) and (II) both are correct, we could say that overall vehicles are ticketed multiple times. So, Option (B) is correct.
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Re: Highway drivers problem cant understand explain [#permalink]

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25 Apr 2013, 03:42
umeshpatil wrote:
Consider, There are 1000 drivers on Maryland highways.
3% i.e. 30 vehicles doesn't have radar detectors with them... (from data in CR)... (I)

Consider, 60 vehicles are ticketed for exceeding the speed limit
33% i.e. 20 vehicles didn't have the radar detectors.. (from data in CR)... (II)

From I & III,
20 vehicles with no radar detectors were out of 30 vehicles. Now consider, If 120 vehicles were ticketed, there would around 40 vehicles with no radar detectors.
Data seems to be inconsistent.

If (I) and (II) both are correct, we could say that overall vehicles are ticketed multiple times. So, Option (B) is correct.

Though the explanation provided by Zarrolou is fine I think yours get the point more clear in THIS scenario or situation.

Clearly the assumption is a gap between premise and the conclusion.

If we have 3% with radar and 97% without radar so WHy we have 33% of ticketed drivers that have the radar ?' why if the first one % is so low the second one is so HIGH?

Only if we have the same driver that do the same thing more than once (3 4 and so on)

So only B have sense.
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Re: Highway drivers problem cant understand explain   [#permalink] 25 Apr 2013, 03:42

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