Driver who equip vehicles with Radar Detectors

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jasourne: Junior | Next Rank: 30 Posts; Posts: 16; Joined: Sun Jul 15, 2012 10:11 pm

by jasourne » Mon Jul 30, 2012 11:15 pm

Q. 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.

OA is [spoiler]B[/spoiler]. Could someone explain please?

Thanks.

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Source: Beat The GMAT — Critical Reasoning | Mon Jul 30, 2012 11:15 pm

vk_vinayak: Legendary Member; Posts: 502; Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members; Thanked: 99 times

by vk_vinayak » Tue Jul 31, 2012 12:21 am

Let's say, R-Vehicles => Vehicles with radar detectors
NR-Vehicles => Vehicles without radar detectors

Argument: 33% of the vehicles ticketed for exceeding the speed were R-Vehicles. Therefore drivers who drive R-Vehicles are more likely to exceed the speed limit than drivers who drive NR-Vehicles.

Premise talks about number of vehicles ticketed and conclusion talks about drivers. We need to fill that gap. Only B fills that gap.

Argument: Drivers of R-Vehicles are likely to exceed the speed because more R-Vehicles have been ticketed.

Assumption: Drivers who are ticketed are more likely to exceed the speed.

- VK

I will (Learn. Recognize. Apply)

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vk_vinayak: Legendary Member; Posts: 502; Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members; Thanked: 99 times

by vk_vinayak » Tue Jul 31, 2012 12:47 am

Just googled the question and found the following link. It has some great insights. Hope it helps.
https://www.manhattangmat.com/forums/og-cr-81-t444.html

- VK

I will (Learn. Recognize. Apply)

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jasourne: Junior | Next Rank: 30 Posts; Posts: 16; Joined: Sun Jul 15, 2012 10:11 pm

by jasourne » Tue Jul 31, 2012 11:06 pm

Thnx vk_vinayak.

The link was helpful in solving my doubt

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Wed Aug 01, 2012 4:13 am

jasourne wrote:Q. 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.

OA is B. Could someone explain please?

Thanks.

Learn to recognize the common flaws.
This CR exhibits a language shift.
The premise is about drivers who get at least ONE -- and perhaps ONLY one -- speeding ticket.
The conclusion is about drivers who exceed the speed limit REGULARLY.
The argument assumes that there is a LINK between these two ideas: that a driver who gets at least ONE speeding ticket exceeds the speed limit REGULARLY.

A useful tool for assumption questions is the negation test.
The correct answer is WHAT MUST BE TRUE for the conclusion to be valid.
Thus, when the correct answer is REVERSED, the conclusion will fall apart.
Any answer choice that fails this test can be eliminated.

Answer choice B negated: Drivers who are ticketed for exceeding the speed limit are LESS likely to exceed the speed limit regularly than are drivers who are not ticketed.
The negation of B trashes the conclusion of the argument. Therefore, B is the necessary assumption: WHAT MUST BE TRUE for the conclusion to be valid.

The correct answer is B.

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sachindia: Master | Next Rank: 500 Posts; Posts: 258; Joined: Fri Jun 22, 2012 4:39 amFollowed by: 3 members; Location: Bengaluru, India; Thanked: 6 times; GMAT Score:640

by sachindia » Fri Aug 31, 2012 6:45 am

negating B

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

So conclusion that
drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not
falls apart because those who equip their vehicles with radar detectors are the ones who were ticketed 33% of the times.

hope my understanding is right..Please correct me if I am wrong.

Regards,
Sach

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