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# Third Kaplan CR ! Very subtle

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Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 12:54
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I am reopening this question. Please explain your answer and especially option C to the max extent.

Air travel is becoming increasingly more
dangerous. In the last year there have been
seven major collisions resulting in over 700
deaths, more deaths than in any previous year.
Which statement, if true, would most weaken
the argument above?
(A) Since the volume of air traffic has been
increasing all the time, an increase in the
number of deaths due to collisions does
not necessarily mean greater danger.
(B) The increase in collisions can be explained
by statistical coincidence, hijackings, and
unusual weather.
(C) Mortality per passenger mile is lower for
air travel than for any kind of surface
transportation.
(D) The increase in deaths due to collision in
air travel has proceeded at a rate identical
to that for deaths in all other major forms
of transportation.
(E) Last year the average number of
passengers per flown plane was
significantly lower than that of previous
years.

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:02
My take on this:

A - Correct: The statement calls the concept of percentage of accidents, not the total number of accidents. An increase in number of total flights, with the rate of accident not changing means that while number of mortality increases, air travel did not necessarily become more dangerous
B - Mention of hijackings explaining the collisions allude to air travel becoming more dangerous
C - Mention of surface transportation makes it out of scope
D - Mention of other forms of transportation makes it out of scope
E - With lower passenger counts last year, while mortality counts are high means that there are more collisions last year than there were in the previous years, supporting the statement.

What do you guys think?

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:06
What is the OA?

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:09
how C is out of scope? If you are not going to travel by air, you would use a surface transport?

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:15
nusmavrik wrote:
how C is out of scope? If you are not going to travel by air, you would use a surface transport?

The question asks us to evaluate whether air travel has become more dangerous on account of increased collisions. Walking might be safer than air travel and surface transport both but that's not what's being evaluated here...

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:16
Hmm, I'm thinking if you compare the mortality rate of air travel with surface travel - you're not addressing how air travel is becoming increasingly dangerous. Mortality per mile might be low compared to surface travel, but it doesn't provide a clue whether it became more dangerous or not in relation to itself only. That's my guess. Idk idk.

Is the OA C? Yikes, show me the light!

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:26
I am thinking someone will go over the fence for C. Either make C as the answer or blot it out

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Re: Third Kaplan CR ! Very subtle [#permalink]

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02 Jul 2010, 13:50
Yes there is a bit confusion between A & C at first place.. But for me A is right. as the question does not discusses about any other means of Travel.

The flaw in the Argument can be better raised by putting question mark on the Base quantity i.e. Volume of Air Travel

For Instance, If There are 5 incorrect answers in previous attempt and 10 in fresh attempt that does not Infers that the Test Taker's ability has decreased, till we don't know the actual no. of questions in the Test.

Same is the case here.. Volume of air travel has increased but proportion of Accidents might be less and thus danger is either less or the same.

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Re: Third Kaplan CR ! Very subtle [#permalink]

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04 Jul 2010, 04:28
I agree that A is the correct answer. Note that A makes the conclusion less likely to be true by introducing a premise that raises doubt on the validity of the comparison between the two years. With A we know that the conclusion is not "apple to apple" given the change in the volume of traffic. C broadens the scope and is not linked to the core conclusion issue "Plane more dangerous = f( increase in collisions) vs. C" Plane more dangerous than other means".

A correct answer has always to be within the conclusion scope and without additional logical leaps, and directly - or through logical implication - challenges the validity of the conclusion even a little bit.

Hope this helps.
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Re: Third Kaplan CR ! Very subtle [#permalink]

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04 Jul 2010, 05:18
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OA is A. Here is the crux :
for example..
earlier, 100 ppl travel and 10 died.
now, 200 ppl travel and 11 died..
does this statistic mean that air travel has become more dangerous than earlier.. ?

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Re: Third Kaplan CR ! Very subtle [#permalink]

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07 Jul 2010, 14:11
The only point that I can think why A is better than C is that C is comparing air travel with other modes of travel to prove that air travel is not dangerous

whereas the argument is expecting to compare air travel with itself to prove that (bit weird though because I feel C is a better contender than A)

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Re: Third Kaplan CR ! Very subtle [#permalink]

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07 Jul 2010, 14:57
Thanks for the explanations. I also got quite confused.
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Re: Third Kaplan CR ! Very subtle [#permalink]

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07 Jul 2010, 21:27
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[quote2nusmavrik]Please explain your answer and especially option C to the max extent.[/quote2]

The author isn't arguing that:

--air travel is a very dangerous form of transportation
or that:
--air travel is more dangerous than other forms of transportation.

If the author was making either of these arguments, then, yes, choice C definitely weakens (actually, the above two conclusions are essentially the same because you would only be regarded as a dangerous form of transportation in consideration of other forms of transportation.)

Instead, the author is arguing:

--air travel is more dangerous than it used to be. Is this different or the same as the above two conclusions?

As another poster astutely pointed out, the author isn't comparing the dangerousness of air travel to that in other forms of travel. Instead, the author is comparing the dangerousness of air travel at two different points in time. Thus, the argument does not include in its scope air travel's comparison to other forms of transportation. Thus, choice C is outside the scope (and, thus, it cannot weaken the argument).

----

For many people (including myself), it is helpful to view arguments as conversations. In weaken questions, you can view the answer choices as other speakers who are all attempting to counter the original arguer as best they can. Your task is to judge the winner. Let us consider answer choice C in this light:

The author is arguing that air travel is more dangerous than it used to be.

Let us say a second speaker riposted:

"yeah, but look: air travel is safer than any other form of transportation".

What would the author say in response? He would say:

"yes, but air travel is more dangerous than it used to be; and nothing you've said discounts that." And, you can tell in the conversation that the author is right: choice C does not discount his claim.

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Re: Third Kaplan CR ! Very subtle [#permalink]

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07 Jul 2010, 23:55
Hey Testluv
Arguments thanks !
I disagree with you only on one thing -
It is not necessary that the correct answer will be in scope. Scope does not matter in strengthening or weakening questions. It matters in the Assumption / Inference though.

C is wrong because of Incorrect comparison (mortality per mile is different from collisions in a volume of traffic). The argument may go on forever since two people are talking on different topics.

Testluv wrote:
[quote2nusmavrik]Please explain your answer and especially option C to the max extent.[/quote2]

The author isn't arguing that:

--air travel is a very dangerous form of transportation
or that:
--air travel is more dangerous than other forms of transportation.

If the author was making either of these arguments, then, yes, choice C definitely weakens (actually, the above two conclusions are essentially the same because you would only be regarded as a dangerous form of transportation in consideration of other forms of transportation.)

Instead, the author is arguing:

--air travel is more dangerous than it used to be. Is this different or the same as the above two conclusions?

As another poster astutely pointed out, the author isn't comparing the dangerousness of air travel to that in other forms of travel. Instead, the author is comparing the dangerousness of air travel at two different points in time. Thus, the argument does not include in its scope air travel's comparison to other forms of transportation. Thus, choice C is outside the scope (and, thus, it cannot weaken the argument).

----

For many people (including myself), it is helpful to view arguments as conversations. In weaken questions, you can view the answer choices as other speakers who are all attempting to counter the original arguer as best they can. Your task is to judge the winner. Let us consider answer choice C in this light:

The author is arguing that air travel is more dangerous than it used to be.

Let us say a second speaker riposted:

"yeah, but look: air travel is safer than any other form of transportation".

What would the author say in response? He would say:

"yes, but air travel is more dangerous than it used to be; and nothing you've said discounts that." And, you can tell in the conversation that the author is right: choice C does not discount his claim.

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Re: Third Kaplan CR ! Very subtle [#permalink]

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08 Jul 2010, 00:13
[quote2nusmavrik]It is not necessary that the correct answer will be in scope. Scope does not matter in strengthening or weakening questions. It matters in the Assumption / Inference though.[/quote2]

thanks for your comment; but I've heard it before. Although it is a fallacious claim from a technical/logical standpoint, it might actually be not bad advice from the standpoint of test-taking strategy. Perhaps that's why I hear people make the claim every once again (i.e., the claim that scope is irrelevant in stn/wkn questions).

But why do you think that?

It may depend on what you mean by "scope".

A necessary condition of scope: "any fact that has to do with the argument's ideas". If a fact has naught do with an argument's ideas, then it can't fall within the scope, and thus cannot strengthen or weaken it.

It is certainly true that choices that seem outside the scope are often correct in stn/wkn questions. (The only reason a choice that is actually within the scope may seem outside the scope is if a student failed to grasp every necessary assumption of the argument). So, one tip I do always give my students is:

"in stn/wkn questions, scope is not your best friend". You shouldn't be quick to eliminate choices for reasons of scope. (In fact, I even have a pet LSAT question that I use to show where the right answer seems outside scope, so students eliminate it; I then show that it is actually squarely within the scope of the argument...let me know if you want to see it!)

However, as a matter of logic and working with the correct definition of scope, a fact has to be within scope in order to stn or wkn; it is a necessary condition to strengthening or weakening.

I can of course be called upon to demonstrate that the accredited response of any officially released GMAT stn/wkn question is within the scope of the argument. Just pick one, and I'll be more than happy to discuss, if you think the exercise will be helpful.

In this particular question, the wrong answer under discussion falls under two categories: outside the scope and irrelevant comparison. Both of these are common wrong answer types in all assumption family questions. Not every irrelevant comparison is outside the scope but this one is.

And of course, a choice may be wrong even if it is within the scope. (That is, being outside the scope is not the only reason a wrong answer can be wrong of course).

(As an aside, many official Kaplan explanations offer "outside the scope" as a common reason why wrong answers to stn/wkn are wrong. Thus, Kaplan's well-funded R&D team views scope as a valid logical reason for eliminating wrong answers in this type of question!)

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Re: Third Kaplan CR ! Very subtle [#permalink]

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08 Jul 2010, 00:51
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But why do you think that? --->

I am not an expert. Still I believe Kaplan should replace the term "scope" with "consistency" when answering strengthening / weakening questions.

Imagine two people arguing - one talking about x and another talking about y. Hence noone can can strengthen weaken / strengthen each other. There wasn't a mutual point. Argument can go on forever and still useless!

An argument can be weakened only on its own terms - unless its a causal argument. I will point that in a bit
In this question "collisions" are used as an argument - then to flaw that reasoning someone should attack collision - Percentages are easier to attack on gmat. So here one can attack since the exact percentage of that causing collision in total volume is unknown we cannot infer anything by hard numbers. Vice-versa someone can attack the rising volume of traffic (choice A) which will lead to conclusion that exact percentage of that causing the collision is unknown. Even if the numbers are increasing - seven major collisions resulting in over 700 deaths.

This one is from Manhattan.
In any passage that takes CORRELATION and concludes CAUSATION, that connection can be destroyed if either:
(1) the causation actually runs the other way around (i.e., the passage concludes that X causes Y, but in actuality Y causes X);
(2) the two correlated things are both results of some third, not considered, confounding factor.

For example :

The number of murder in American cities is correlated with large number of churches in the cities. Hence church cause murder in the cities.

There is a strong correlation between the # of churches and the # of murders in American cities: the more churches, the more murders. However, there is no causation at work here (churches don't cause murders, and murders don't cause the building of churches), because both of these factors are caused by a third factor: the SIZE of the city. (larger cities have both more churches and more murders.)

This third factor is the one OUTSIDE the scope or not mentioned in the passage. It works wonderfully here

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Re: Third Kaplan CR ! Very subtle [#permalink]

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08 Jul 2010, 01:33
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Thank you for your well thought-out response nusmavrik! As a teacher, I love to see students tackle the concepts so willingly, and think about them in such great detail.

As I suspected, and as you suggest in your first paragraph, our disagreement is one of semantics, and is likely academic. However, please allow me the opportunity to re-interpret your evidence so that it can just as easiliy suppot my view. Your evidence is a great example:

Quote:
The number of murder in American cities is correlated with large number of churches in the cities. Hence church cause murder in the cities.

There is a strong correlation between the # of churches and the # of murders in American cities: the more churches, the more murders. However, there is no causation at work here (churches don't cause murders, and murders don't cause the building of churches), because both of these factors are caused by a third factor: the SIZE of the city. (larger cities have both more churches and more murders.)

This third factor is the one OUTSIDE the scope or not mentioned in the passage. It works wonderfully here.

Now, another way of looking at this is how the author is reasoning; not just what was and was not "mentioned" in the passage. That the author failed to consider alternative causation (ie, "third factor") is a flaw in reasoning...Thus, any fact that points to an alternative cause weakens (while any choice that removes an alternative cause strengthens) the argument by reference to this flaw in reasoning. Facts that have to do with the author's flaw in reasoning ipso facto have to do with the author's reasoning. Thus, facts that deal with overlooked causes lie within the ambit or scope of the author's reasoning/argument.

While they may SEEM outside the scope they are not truly outside the scope. In other words, on my view, just because a fact is not mentioned, does not mean that it is outside the scope because that fact still may have to do with the autor's reasoning. Considering the question at hand, we can say that other modes of transportation don't have anything to do with the author's argument--choice C is outside the scope.

In short: I am taking "scope" to mean something that has to do with the author's reasoning explicitly or implicitly. You seem to be taking "scope" to mean something that was explicitly mentioned in the argument.

(I should also reiterate that scope is not your best friend in stn/wkn questions for the reason I discussed in my post above. I should also emphasize that a fact NOT mentioned in the passage may still stn or wkn an argument.)

However, our debate is very academic, and not necessarily most helpful. What is important is that you arrive at an effective way of looking at it, and it sounds as though you have. So, let me leave you with a modified version of MGMAT's tip:

In passages that CORRELATION and conclude CAUSATION, that connection can be destroyed in three ways:
(1) a choice that suggests alternative causation (most common on the GMAT)
(2) a choice that suggests that correlation is merely a coincidence
(3) the causation actually runs the other way around (i.e., the passage concludes that X causes Y, but in actuality Y causes X) (least common, and at Kaplan we call this "reversal of causality")

Some comments:

(1) and (2) are closely related. if, as per (2) a choice suggests the connection between x and y is a mere coincidence, then because everything has a cause, there must be some other cause--(1) is strictly implied. That's probably why MGMAT lumps (1) and (2) together. I've found that many students benefit from viewing (1) and (2) separately because, in their first instance, some answer choices directly suggest alternative cause while some other choices (fewer but some) suggest coincidence.

Finally, it is an oversimplification to say that my (3)--reversal of causality--applies to ANY correlationbased causal argument. There are two types of correlation:

chronological (x before y)
simultaneous (x at the same time as y)

Reversal of cauasality CANNOT apply to chronological arguments. Let us consider an example:

"I had a headache. I took a tylenol, and my headache then went away. Thus, because I took the tylenol BEFORE the relief from my headache, my taking of the tylenol must have CAUSED my relief from the headache."

Let's now reverse this, and see if it makes any sense:

"The relief from my headache was the cause of my taking the tylenonl."

Does the argument make sense when reversed? Of course not. The temporal aspect prevents it from making sense. Thus, arguments of causation that are based on chronological correlation cannot be intelligibly reversed.

Of course, arguments of causation based on simultaneous correlation can be sensically reversed:

Did you get good grades because the teachers liked you or is it because the teachers liked you that you got good grades?

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Re: Third Kaplan CR ! Very subtle [#permalink]

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I will go with A as it is weakning the argument by saying "Since the volume of air traffic has been increasing all the time, an increase in the number of deaths due to collisions does not necessarily mean greater danger." C is out of scope because it says "Mortality per passenger mile is lower for air travel than for any kind of surface
transportation". Here any other means of transport is not important. Even if C option is true/false it does not impact the main argument under consideration.
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Re: Third Kaplan CR ! Very subtle [#permalink]

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08 Jul 2010, 09:46
Testluv,
Thanks for your valuable inputs ! I must say, last night I gave a real thought on "scope". Its abstract but one should be able to discern the "scope shifts" or subtle shift in focus ! In a weakening question I have seen if answer choice is claiming to destroy the argument completely then its a gmat trap - no accidents here As choice C in this argument is claiming to do but actually NOT.

I should also emphasize that a fact NOT mentioned in the passage may still stn or wkn an argument. ---> I truly agree with this point.

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Re: Third Kaplan CR ! Very subtle [#permalink]

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nusmavrik wrote:
how C is out of scope? If you are not going to travel by air, you would use a surface transport?

correct but how does that weaken the argument ..........how can that explain that Air travel is not becoming increasing dangerous .........It can only say that it is dangerous .......

I had seen the question and marked it wrong ....I don't remember which option

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Re: Third Kaplan CR ! Very subtle   [#permalink] 04 Aug 2010, 00:52

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