Silver Bullet Train

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Silver Bullet Train

by anirudhbhalotia » Sat Apr 09, 2011 3:20 am
Source - GMAT Hacks

Advertisement in the Harptown Train Station:

The Harptown Transport Society reports that the Silver Bullet train has the fewest delays per rush-hour period of any high-speed train. This shows that the Silver Bullet train is one of the most efficient trains currently in use.

Which of the following, if true, most seriously weakens the argument in the advertisement?
(A) The Harptown Transport Society report listed many non-high-speed trains in other metropolitan areas that were more frequently delayed than the Silver Bullet train.

(B) In recent years more travelers have regularly ridden the Silver Bullet train than any other high-speed train.

(C) High-speed trains are more likely to be delayed during rush hour than any other type of train.

(D) The difference between the number of delays on the Silver Bullet train and that for other high-speed trains is quite pronounced.

(E) The Harptown Transport Society updates its findings regarding train delays only once a year.

OA - C


Why is E not right?
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by HSPA » Sat Apr 09, 2011 3:46 am
delay/hour = less => average speed is more.

other trains have more delay = less avg speed, Silverbullet is efficient because others are cheap..

E is out of scope.. Argument is not regarding records..We donot bother about how frequent the records are updated by Harptown transport
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by maihuna » Sat Apr 09, 2011 3:49 am
Are u sure, C is OA, I think D looks fine. E is wrong as it is disputing data collection which is outside the scope of the argument.
anirudhbhalotia wrote:Source - GMAT Hacks

Advertisement in the Harptown Train Station:

The Harptown Transport Society reports that the Silver Bullet train has the fewest delays per rush-hour period of any high-speed train. This shows that the Silver Bullet train is one of the most efficient trains currently in use.

Which of the following, if true, most seriously weakens the argument in the advertisement?
(A) The Harptown Transport Society report listed many non-high-speed trains in other metropolitan areas that were more frequently delayed than the Silver Bullet train.

(B) In recent years more travelers have regularly ridden the Silver Bullet train than any other high-speed train.

(C) High-speed trains are more likely to be delayed during rush hour than any other type of train.

(D) The difference between the number of delays on the Silver Bullet train and that for other high-speed trains is quite pronounced.

(E) The Harptown Transport Society updates its findings regarding train delays only once a year.

OA - C


Why is E not right?
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by maihuna » Sat Apr 09, 2011 3:50 am
I am somewhere lost in this cheapness mess, can u please re-elaborate.
HSPA wrote:delay/hour = less => average speed is more.

other trains have more delay = less avg speed, Silverbullet is efficient because others are cheap..

E is out of scope.. Argument is not regarding records..We donot bother about how frequent the records are updated by Harptown transport
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by rohu27 » Sat Apr 09, 2011 3:53 am
Gmat hacks says the below (only if someone can explain this- i dnt get it)

This is a classic example of a scope shift. The evidence (the first sentence) compares the Silver Bullet to other "high-speed trains." The conclusion compares it to all trains. Just because a train has few delays relative to other high-speed trains doesn't mean it has few delays (or is "efficient") compared to ALL trains. Look for a choice that points out the scope shift.

Choice (C) does that. If high-speed trains are often delayed, then argument is weakened. It exposes the flaw in the argument, which is along the lines of "Alex is the smartest 'D' student in the class." (C) is correct.

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by HSPA » Sat Apr 09, 2011 4:45 am
maihuna wrote:I am somewhere lost in this cheapness mess, can u please re-elaborate.
HSPA wrote:delay/hour = less => average speed is more.

other trains have more delay = less avg speed, Silverbullet is efficient because others are cheap..

E is out of scope.. Argument is not regarding records..We donot bother about how frequent the records are updated by Harptown transport
cheap means.. I meant other high speed trains are more delayed
A trains travels 40 miles in 40 min and halts for 20 min.. then speed of train = 40miles/hour
silverbullet covers 45miles in 60minutes... Argument says silverbullet is > other trains
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by David@VeritasPrep » Sat Apr 09, 2011 5:45 am
Received a PM on this one...

This is not only as they say a "classic example of scope shift." This is also a classic example of a problem that could use a little editing.

The conclusion says "the Silver Bullet train is one of the most efficient trains currently in use." The evidence that supports this is "the Silver Bullet train has the fewest delays per rush-hour period of any high-speed train."

But what does "efficient" mean in the conclusion? I read that and I was thinking "fuel-efficient." As in burns less fuel per mile. Fewer delays does not mean efficient.

Now if we accept that the definition of efficient is fewer delays then we can weaken with choice C. This is because we are saying that this train has among the least delays of all trains. Why? Because it has the least delays of one type of train. What if that overall type of train is the worst? Then you are the best of the worst -- not so good!

Let me give an example. What if I say that my brand of cookie (biscuit for the Brits) is the healthiest cookie on the market. And then I say it is one of the healthiest things you can eat. To weaken we just point out that cookies as a category are not very healthy compared to fruits/ veggies etc and we have weakened.
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by mundasingh123 » Sun Apr 10, 2011 2:22 am
David@VeritasPrep wrote:Received a PM on this one...

This is not only as they say a "classic example of scope shift." This is also a classic example of a problem that could use a little editing.

The conclusion says "the Silver Bullet train is one of the most efficient trains currently in use." The evidence that supports this is "the Silver Bullet train has the fewest delays per rush-hour period of any high-speed train."

But what does "efficient" mean in the conclusion? I read that and I was thinking "fuel-efficient." As in burns less fuel per mile. Fewer delays does not mean efficient.

Now if we accept that the definition of efficient is fewer delays then we can weaken with choice C. This is because we are saying that this train has among the least delays of all trains. Why? Because it has the least delays of one type of train. What if that overall type of train is the worst? Then you are the best of the worst -- not so good!

Let me give an example. What if I say that my brand of cookie (biscuit for the Brits) is the healthiest cookie on the market. And then I say it is one of the healthiest things you can eat. To weaken we just point out that cookies as a category are not very healthy compared to fruits/ veggies etc and we have weakened.
Hi David , Why E isnt right ?
Pointing out a flaw in the premise isnt wrong .
Throwing doubts on the manner in which the survey was conducted , in case of CRs based on surveys
isnt inappropriate

E says the finds are updated once a year.
What if the update took place 6 months back and Silver Bullet has been beaten in terms of efficiency by another train, Gold Flash , isnt the conclusion weakened ?
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by anirudhbhalotia » Sun Apr 10, 2011 6:28 am
mundasingh123 wrote:
David@VeritasPrep wrote:Received a PM on this one...

This is not only as they say a "classic example of scope shift." This is also a classic example of a problem that could use a little editing.

The conclusion says "the Silver Bullet train is one of the most efficient trains currently in use." The evidence that supports this is "the Silver Bullet train has the fewest delays per rush-hour period of any high-speed train."

But what does "efficient" mean in the conclusion? I read that and I was thinking "fuel-efficient." As in burns less fuel per mile. Fewer delays does not mean efficient.

Now if we accept that the definition of efficient is fewer delays then we can weaken with choice C. This is because we are saying that this train has among the least delays of all trains. Why? Because it has the least delays of one type of train. What if that overall type of train is the worst? Then you are the best of the worst -- not so good!

Let me give an example. What if I say that my brand of cookie (biscuit for the Brits) is the healthiest cookie on the market. And then I say it is one of the healthiest things you can eat. To weaken we just point out that cookies as a category are not very healthy compared to fruits/ veggies etc and we have weakened.
Hi David , Why E isnt right ?
Pointing out a flaw in the premise isnt wrong .
Throwing doubts on the manner in which the survey was conducted , in case of CRs based on surveys
isnt inappropriate

E says the finds are updated once a year.
What if the update took place 6 months back and Silver Bullet has been beaten in terms of efficiency by another train, Gold Flash , isnt the conclusion weakened ?
This is exactly my reasoning too.

I think the question is not very clear..lots of assumptions as to what does efficient means and what exactly is the questions about.
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by David@VeritasPrep » Sun Apr 10, 2011 7:50 am
Mundasingh -

That is very interesting point you make. The conclusion does have the word "currently" in it. So I suppose that unless they update very frequently the "currently" might be suspect.

But you have said something here that is not quite right - you in fact cannot attack a premise on the GMAT. You can say that the premise does not lead to the conclusion, but you cannot attack a premise itself.

I would say that in a question that has a clearer logical process that this would not be the right answer. That another answer is intended here. You can tell when they want you to attack the methods. It is tough to explain but the stimulus will give you some indication -- or the question stem, "The methodology is flawed for which of the following reasons."

If not, if it just a sort of normal problem they usually are not focused on the methodology.
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by anirudhbhalotia » Sun Apr 10, 2011 8:12 am
David@VeritasPrep wrote:Mundasingh -

That is very interesting point you make. The conclusion does have the word "currently" in it. So I suppose that unless they update very frequently the "currently" might be suspect.

But you have said something here that is not quite right - you in fact cannot attack a premise on the GMAT. You can say that the premise does not lead to the conclusion, but you cannot attack a premise itself.

I would say that in a question that has a clearer logical process that this would not be the right answer. That another answer is intended here. You can tell when they want you to attack the methods. It is tough to explain but the stimulus will give you some indication -- or the question stem, "The methodology is flawed for which of the following reasons."

If not, if it just a sort of normal problem they usually are not focused on the methodology.
Are these kind of questions usually cropping up in actual GMAT? Or this is rarest of the rare.
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by David@VeritasPrep » Sun Apr 10, 2011 10:20 am
No this question will never be on the GMAT!!!!!

Remember those questions are edited so many times - it costs nearly $3000 US to write a single GMAT question. This one is poorly edited.

What would actually appear on the test is a "shift in scope."

So "I have the best lawn in the neighborhood so it must be among the best in the city."

You can see that it might be the case that my neighborhood has the worst lawns in the whole city. So that is the shift. Really could call it "over generalization."
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by Target2009 » Mon Apr 11, 2011 11:11 am
David@VeritasPrep wrote:No this question will never be on the GMAT!!!!!
Remember those questions are edited so many times - it costs nearly $3000 US to write a single GMAT question.
Wow .. Now i feel how precious OG questions are. :)

BTW thanks David for detailed explanation.
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by mundasingh123 » Mon Apr 11, 2011 9:06 pm
David@VeritasPrep wrote:Mundasingh -

That is very interesting point you make. The conclusion does have the word "currently" in it. So I suppose that unless they update very frequently the "currently" might be suspect.

But you have said something here that is not quite right - you in fact cannot attack a premise on the GMAT. You can say that the premise does not lead to the conclusion, but you cannot attack a premise itself.

I would say that in a question that has a clearer logical process that this would not be the right answer. That another answer is intended here. You can tell when they want you to attack the methods. It is tough to explain but the stimulus will give you some indication -- or the question stem, "The methodology is flawed for which of the following reasons."

If not, if it just a sort of normal problem they usually are not focused on the methodology.
So David, In a weaken cR / Flaw in reasoning CR , i cant attack a premise but only the conclusion unless i have been asked to attack a premise in the question stem , ie "the methodology is flawed because "
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by David@VeritasPrep » Wed Apr 13, 2011 10:08 am
That is correct do not EVER attack or otherwise doubt the premises. Two rules of the GMAT -- on Data Sufficiency the statements are always true right? Those can never be false. Same with the premises in critical reasoning.

It is the link between the premises and the conclusion that you have to focus on. If the premise tells you that "Touching a frog causes warts" you have to accept it. If the conclusion is "Therefore all warts are the result of touching frogs" you do not so much attack that conclusion as the link between the two. You can say, "wait a minute - the evidence is that ONE cause of warts is touching a frog this does not mean it is the only cause(as the conclusion indicates). So you will have weakened the argument or pointed out the flaw or whatever the question asks by breaking down the LINK BETWEEN THE PREMISE AND CONCLUSION.

Even if they ask for a flaw in the methodology you will not DOUBT a premise. If the premise says that two people were interviewed and they both are vegetarians and you conclude that all people are vegetarians it is not that you DOUBT the premise. Instead you say, "Even if premise is true it does not lead to the conclusion." So what is the problem in the methodology? Too few people interviewed right? Over-generalization? But this is not ATTACKING the premise it is using the premise as a weapon against the argument. It is after all the premise that let us know only two people were interviewed!!

Hope that helps

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