Air travel is becoming increasingly more dangerous. In the last year

i wuld go with option E(seems best)

since in option A its 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

if the volume of air traffic is increasing and it is resulting in collisions dsnt it state that air travel has become more dangerous...

arvs212,.

No, it doesnt become increasingly dangerous..
because the arguments says that the increase in the number of deaths mean more danger..
but the flaw is that they didnt consider the no of the passengers that were travelling..

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.. ?

A is answer.
E is wrong. For example, previous years have 100 passengers with 5 death each year (5% chance of death). Last year has lesser passengers than previous years, let's say 70 passengers and with 7 deaths (10% chance of death). Therefore E strengthens the conclusion.

ANS : A
(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.

clearly weaken because more accidental death not mean more danger.

(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. -> Weakens. Hence the answer
(B) The increase in collisions can be explained by statistical coincidence, hijackings, and unusual weather. -> Strengthens the argument
(C) Mortality per passenger mile is lower for air travel than for any kind of surface transportation. -> Out of scope. Comparison with any other means of transport is unnecessary.
(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. -> Strengthens the argument
(E) Last year the average number of passengers per flown plane was significantly lower than that of previous years. ->Strengthens the argument

A must be the answer as according to it , it states that the air trafic has increased and there are more passengers now so the increased no of passenger death is the effect of that .

(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. ultimately it supports

(C) Mortality per passenger mile is lower for air travel than for any kind of surface transportation.out of scope

(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.we should be concentrating about air travel only. out of scope

(E) Last year the average number of passengers per flown plane was significantly lower than that of previous years. nothing to do with average no of passengers. out of scope

I am reopening this question. Please explain your answer and especially option C to the max extent.

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.. ?

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.

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.

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!)

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

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:





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?

(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.
Only statement which says passenger casuality per air trqavel may actually have reduced, hence air travel is as safe as before if not safer.


(B) The increase in collisions can be explained by statistical coincidence, hijackings, and unusual weather.
This actually supports that Air travel has become more dangerous ,with supporting factors such as hijackings etc.

(C) Mortality per passenger mile is lower for air travel than for any kind of surface transportation.
Incorrect comparison between air and other modes of travel, comparison is between air travel of current and previous years.

(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.
Incorrect comparison between air and other modes of travel, comparison is between air travel of current and previous years.

(E) Last year the average number of passengers per flown plane was significantly lower than that of previous years.
This actually supports the claim that Air travel has become more dangerous. With less people per aircraft and increase in the number of casualities, it means that more number of planes are involved in mishaps.

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.

----
The gist of the argument / paraphrase is that air travel is becoming more dangerous on the basis of evidence of a major death toll last year vs. previous years from air collisions. We need to recognize the causal link. To weaken this link, one would expect the right answer to talk about alternative reasons for the conclusion (air travel more dangerous) or to the premise (collisions) or shows that the conclusion and premise can coexist peacefully. Anything that really challenges this link without requiring additional information or logical leap. That in mind, lets attack the answer choices:

A) sounds promising. Lets keep as contender and get back to it later
B) We dont care about explanation for collisions. We are concerned about their interpretation as increased danger. In any case, it does strengthen the argument if anything else
C) We dont care about comparison. It still be high enough to be dangerous or it could be low. We dont know
D) We are not concerned with comparison. The conclusion does not say it is the most dangerous form of transportation, and we dont know other rates. We are forced to assume, so out
E) Intriguing, rather strengthen but need to assume anyway.

Seems A is best of all.

Hope this is helpful.

Logically, IMHO the best answer is A.

B - Weakens the argument vs *other* forms of transport, just doesn't weaken the argument when simply talking about *air* transport, which is the subject at hand.
C - That's well and good, but (getting back to topic) the danger to air travel might nonetheless still be getting more dangerous.
D - Fine, but then by extension of the argument *all* forms of transport are getting more dangerous.
E - This actually strengthens the argument (ie, if fewer people are flying *and* collisions are up).

If there's any hole in my reasoning, I welcome comments. As I can benefit from it too.
(Thanks in advance!)