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Traffic Inspector Question - Answer Not Available

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by stevennu » Sun Jun 23, 2013 12:23 pm
This question is on the Magoosh eBook. When I clicked the link, it said the question is no longer available. I'm trying to work through the question but would like confirmation that my answer choice is correct. The question and answer choices are listed below.

Traffic Inspector: Serious traffic accidents on weekday mornings on Highway 31 always result in major congestion. Highway 31 was especially congested Tuesday morning, so there must have been a serious accident.

Which of the following contains questionable reasoning that most closely parallels that in the argument above?

A) Smoking lowers one's life expectancy; thus, if Al quits smoking, he will extend his life.

B) When the weather is nice, Scotta and Dan play tennis. Scott and Dan played tennis today, so the weather must have been nice.

C) Whenever a city builds a new highway, revenue from public transit decreases. The major of Oakville wishes to increase public transit revenue, so he will not build a new highway.

D) Every time Barbara's dog wants to go for a walk, he sits by the front door. Barbara's dog is not sitting by the front door, so he must not want to be walked.

E) Dr. Fong's dentistry practice always experiences a surge in appointments after Halloween. Halloween is approaching, so Dr. Fong should expect a surge in appointments.


My analysis is that the traffic inspector's original argument is circular in nature. Serious traffic on weekday = always results in congestion. Congestion on the highway = accident.

The answer choice closest (parallels) to the above statement in my opinion is (A). My reasoning is that there are other factors that could result in a decreased life expectancy for Al even if he stops smoking. What if Al is an meth addict, or what if Al is a meth addicted stuntman aboard a crab fishing boat? Even if he quits smoking, I think it's safe to assume that there are other factors contributing to life expectancy.

Can anyone chime in?
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Source: — Critical Reasoning |

by srcc25anu » Sun Jun 23, 2013 1:14 pm
The argument is of the strcture:
Premise: If A (serious accident) THEN B (major congestion)
Conclusion: If B (major congestion) THEN A (serios accident)

If we analyze Opetion B, we see a similar parallel and flawed reasoning
Prem: If A (nice weather), THEN B (S & D play tennis)
Concl: If B (S & D play tennis), THEN A (nice weather)

Hence IMO it should be B

Any experts differ on this?
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by David@VeritasPrep » Sun Jun 23, 2013 5:30 pm
This is a simple formal logic problem and would not appear in this form on the GMAT.

The posting above is correct. The answer is B. It reverses the sufficient and the necessary condition in the same way that the stimulus does.

Choice A is not reversing the sufficient and the necessary it is negating them. So that is different. A says " if smoking therefore lower life expectancy" The is says "if not smoking then not lower life expectancy." This is simply negating each part of the argument and that is not logically valid. You have stated the reasons why this is not valid --- your meth addicted fisherman is an extreme case....
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