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national speed limit

by aj5105 » Thu Sep 11, 2008 10:37 am
After the national speed limit of 55 miles per hour was imposed in 1974, the number of deaths per mile driven on a highway fell abruptly as a result. Since then, however, the average speed of vehicles on highways has risen, but the number of deaths per mile driven on a highway has continued to fall.
Which of the following conclusions can be properly drawn from the statements above?
(A) The speed limit alone is probably not responsible for the continued reduction in highway deaths in the years after 1974.
(B) People have been driving less since 1974.
(C) Driver-education courses have been more effective since 1974 in teaching drivers to drive safely.
(D) In recent years highway patrols have been less effective in catching drivers who speed.
(E) The change in the speed limit cannot be responsible for the abrupt decline in highway deaths in 1974.
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by banker1 » Thu Sep 11, 2008 11:50 am
IMO: C

We want to draw a conclusion based on the passage, specifically:
Since then, however, the average speed of vehicles on highways has risen, but the number of deaths per mile driven on a highway has continued to fall.

After reading the passage I immediately thought the following:
1. cars are safer now than they were
2. people are safter/ better drivers now than they were
3. people are driving more

(C) fits what I concluded

(A) is not really a conclusion IMO

(B) is tricky. With deaths held constant, 10 deaths over 10 miles is 1 death per mile. 10 deaths over 5 miles is 2 per mile. Mileage driven would have to increase for the number of deaths per mile to decrease (10 deaths over 20 miles is .5 deaths per mile). Since the passage does not mention anything about the number of deaths decreasing, just the number of deaths per mile I did not think this was the best answer.

(D) irrelevant

(E) is not really a conclusion IMO

What is the OA?
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by sethids » Thu Sep 11, 2008 12:47 pm
I believe the answer should be A.

A speed limit was imposed and the number of deaths per mile driven fell abruptly.
However, the average speed has risen but at the same time the number of deaths per mile has fallen.
This means that the speed limit alone is not having an affect on the decrease in the number of deaths per mile. There is another factor contributing to it.

For e.g. maybe the people are driving a lot. Prior to 1974, if the total number of miles driven was 100,000 and the number of deaths was 100. Deaths per mile is 0.001.
Now if the number of deaths is 1000 but the miles driven is 100,000,000 then the number of deaths per mile is 0.00001.
This number has fallen because of the increase in the number of miles driven.

According to me, the clue to catch in the question is "deaths per mile".

B. Not supported by the premise.
C. Out of scope. No information about driver-education is offered.
D. No information and out of scope.
E. It is too narrow and claims that the change in speed limit cannot be responsible. This could be responsible but may not be completely responsible.
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by banker1 » Thu Sep 11, 2008 1:08 pm
sethids wrote:I believe the answer should be A.

A speed limit was imposed and the number of deaths per mile driven fell abruptly.
However, the average speed has risen but at the same time the number of deaths per mile has fallen.
This means that the speed limit alone is not having an affect on the decrease in the number of deaths per mile. There is another factor contributing to it.

For e.g. maybe the people are driving a lot. Prior to 1974, if the total number of miles driven was 100,000 and the number of deaths was 100. Deaths per mile is 0.001.
Now if the number of deaths is 1000 but the miles driven is 100,000,000 then the number of deaths per mile is 0.00001.
This number has fallen because of the increase in the number of miles driven.

According to me, the clue to catch in the question is "deaths per mile".

B. Not supported by the premise.
C. Out of scope. No information about driver-education is offered.
D. No information and out of scope.
E. It is too narrow and claims that the change in speed limit cannot be responsible. This could be responsible but may not be completely responsible.
After rereading the passage and your reasoning I agree (A) is the best answer. I fell into what I call the "scope" trap. As you said, there is no mention of driver education, other factors (not explicitly driver education) are probably the cause of the reduction of deaths.
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by aj5105 » Fri Sep 12, 2008 4:16 am
I appreciate your explanation.
OA is A.

But the problem is - I chose A in my second attempt.But,i get no second chance in my exam.The whole thought process should happen within 1.5 mins.That's a challenge.

IMO,it's certainly not practical for us to have such a detailed thought process during the exam.So,what's the plan for that?


sethids wrote:I believe the answer should be A.

A speed limit was imposed and the number of deaths per mile driven fell abruptly.
However, the average speed has risen but at the same time the number of deaths per mile has fallen.
This means that the speed limit alone is not having an affect on the decrease in the number of deaths per mile. There is another factor contributing to it.

For e.g. maybe the people are driving a lot. Prior to 1974, if the total number of miles driven was 100,000 and the number of deaths was 100. Deaths per mile is 0.001.
Now if the number of deaths is 1000 but the miles driven is 100,000,000 then the number of deaths per mile is 0.00001.
This number has fallen because of the increase in the number of miles driven.

According to me, the clue to catch in the question is "deaths per mile".

B. Not supported by the premise.
C. Out of scope. No information about driver-education is offered.
D. No information and out of scope.
E. It is too narrow and claims that the change in speed limit cannot be responsible. This could be responsible but may not be completely responsible.
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by sethids » Fri Sep 12, 2008 6:47 am
The plan is to look for clues that the question offers like I have mentioned the clue in my earlier post.

I did not do this calculation to reach the correct answer but that should flow logically.
The first thing that should come to the mind regarding these kind of questions is to analyze if a cause is having the desired affect. If no then why not. Could there be any other factors that could influence the circumstances. And if it does have the desired effect, then can we conclude that only the particular cause was 100% responsible for the effect.

In this question for e.g. the speed limit was imposed and the number of deaths per mile decreased. But the number of deaths per mile after that continued to decreased in spite of increasing average speeds. This indicates that the speed limit is not 100% responsible for the decrease in deaths per mile.

HTH
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by niraj_a » Fri Sep 12, 2008 9:48 am
banker1,

that is true, i chose A too, and was able to eliminate C,D, and E pretty quickly simply because outside information is not allowed in determine the conclusion CRs.
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by john83.amar » Wed May 11, 2016 5:00 am
In my opinion A is the most logical one
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