To combat human error involved in air traffic control, Miro

Dear w1ck3d64,
Well, there are a few problems with (A). One of them, as you say --- it's a one-off specific case; any bizarre exceptional thing could happen in a one-off special case. Secondly, we don't know that these planes were the DC-10's with the warning light installed: they could have been any two planes, Air Transylvania or whatever. Finally, when were the warning lights installed? Recently. When did this near collision happen? Recently. Did it happen before or after the DC-10's had warning lights installed? We have no way of knowing. If it happened before the warning lights were even installed, then it certainly doesn't constitute an objection to the efficacy of the warning lights. All this uncertainty means that (A) is not a particular effect objection. That's why it's out.

GMAT CR questions are often written so that wrong answers are tempting. For example, one tempting strategy this answer choice used was a general statement about "two planes", without any indication that the planes were the kind of planes discussed in the prompt. The prompt was about a very specific model of plane, not planes in general. The more you can watch details such as this, the more you will be able to eliminate tempting wrong answers.

Does all this make sense?
Mike

The question is quite straight forward if you keep your eye on the conclusion:

Conclusion: If the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane.

We have to weaken it. That is, we have to establish that red light could be off and still there could be another plane less than three mins flying time away from this plane.
(A) is irrelevant to our conclusion.
(C) weakens the conclusion.
(C) The anti-collision device only signals planes of oncoming directions, not those planes that are flying in parallel.
If anti collision device ignores planes flying parallel, the light could be off but there could be a plane flying parallel to this one which could be less than 3 mins flying time away.

Answer (C)

Hi,

I narrowed down to B and C. but finally picked b.

is B wrong just because there wont be any collison but onboard injuries? We aren't concerned about board injuries as of now , only the collisons...right???

Or The argument mentions 3 minutes is suffcient to manuver.


-h

When we strengthen/weaken an argument, we need to strengthen/weaken the conclusion.
Here the conclusion says "If the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane."

Whether 3 mins is enough time to maneuver is none of our concern. We only want know that when the light is off, is the plane at least 3 mins away from every other plane?
(C) tells us that it may not be and hence our conclusion is weakened.

Focus on the conclusion.

Went with C as its. The best weakener from the choices.
A is talking about air traffic controllers and 1.5 minutes which is irrelevant to the argument.
B is too weak itself to weaken the argument:it has 'in certain cases' and 'may be'.
In D,okay the. Lights don't turn on simultaneously.they might turn on with a very little (negligible) time diff.
In E how is it weakening?It is merely saying that there might be other models having the equipment.So it's good of other models have it and it works.But this isn't weakening the conclusion that 'if red light is off,the plane is necessarily 3 min away from another one.
Only C weakens the conclusion by saying that if a plAne might be parallel and therefore very close to another (less than 3 min close)DC-10 and still the red light won't go on.

Posted from my mobile device

Actually the explanation to justify answer choice 'C' is flawed (in my opinion). The answer choice 'C' is incorrectly worded to say parallel..technically speaking parallel means the planes will never collide...so in that case you wouldn't need the detectors at all...if the answer choice would have specifically said side-by-side then ans choice 'C' would have made sense...anyway this is my 2-cents worth...

Dear p2bhokie,
With all due respect, my friend, you are confusing mathematics with the real world. In mathematics, for example, in geometry, we only use the word "parallel" to denote absolutely strictly parallel; if two lines are even a millionth of a degree off from being parallel, then in geometry they are not parallel.
In the real world, two planes "flying in parallel" mean two planes flying in more or less the same direction, more or less side-by-side. This is a rough, approximate term, not the rigorously precise term we find in geometry. Arguably, it would impossible for planes (or anything in the real world) to be perfectly mathematically parallel. Planes flying "in parallel" may be gradually approaching or receding. Nothing in real life has the same degree of rigor that we find only in the abstract precision of mathematics.
Does all this make sense?
Mike

To combat human error involved in air traffic control, Miro Jets Inc. has recently installed each of its DC-10 passenger planes with a special anti-collision device. The device alerts the DC-10, via a red light, when another plane is slightly more than three minutes away from a potential collision. Aviation experts at Miro Jet Inc. have determined that three minutes is ample time for a plane to divert its respective flight paths to avoid a collision. Therefore, if the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane.

Which of the following, if true, most fundamentally calls into question the aviation analyst’s argument?

(A) Recently, a near collision in which both planes were less than 90 seconds flying distance from each other was averted only by the prompt actions of air traffic controllers. - Thought a near collision was averted by prompt actions of ATC, it would not call into question anti-collision device, since this was a single incidence and we don't have the details of the incidence

(B) Some aviation experts warn that in certain cases three minutes may not provide sufficient time for aircrafts to maneuver without causing onboard injuries. - It might have called the device into question, had the sentence mentioned Collision and not injuries. This becomes out of scope

(C) The anti-collision device only signals planes of oncoming directions, not those planes that are flying in parallel. - Aaaahhh... What if the planes are near parallel ? They might collide and the device won't warn. - This could be a good choice

(D) When two DC-10’s approach each other the red lights on each aircraft do not necessarily turn on simultaneously. - Even if one of the planes is alerted, the collision can be averted.

(E) The DC-10 is not the only aircraft model to have been installed with the anti-collision device. - This would just mean that only DC-10 planes are collision-safe - Out of scope

Hope this helps

mikemcgarry Hey mike what's wrong with D. We have to weaken the conclusion which says If red light is off our plane has more than 3 mins of distance with other plane. But if lights of plane on at different time then the plane whose light on later will have less than 3 mins. thus it will weaken conclusion too.

Dear jaskarn singh,
I'm happy to respond.

Here's the prompt again. Notice the highlights.
To combat human error involved in air traffic control, Miro Jets Inc. has recently installed each of its DC-10 passenger planes with a special anti-collision device. The device alerts the DC-10, via a red light, when another plane is slightly more than three minutes away from a potential collision. Aviation experts at Miro Jet Inc. have determined that three minutes is ample time for a plane to divert its respective flight paths to avoid a collision. Therefore, if the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane.

Which of the following, if true, most fundamentally calls into question the aviation analyst’s argument?


Now, here's (D).
(D) When two DC-10’s approach each other the red lights on each aircraft do not necessarily turn on simultaneously.

Remember, GMAT CR, we have to assume that premises given in the prompt are true. Notice, the prompt doesn't say that the lights go on when the two planes are EXACTLY three minutes away. No, instead, the lights go on when the planes are "slightly more" than 3 minutes away. What does this mean?
Suppose Planes X & Y are approaching each other. When the planes are 3:05 away from each other, the red light goes on in Plane X. When the planes are 3:02 away from each other, the red light goes on in Plane Y. Thus:
(a) in both planes, the light goes on slightly before 3 minutes away
(b) the lights do not turn on simultaneously in the two aircrafts
(c) by the time the two planes are exactly 3 minutes apart, both have the red light on.
Thus, the conclusion is not threatened at all by answer choice (D), as long as we don't change any of the premises.

Does all this make sense?
Mike

DC 10: Spl. A.C.D. -> ↓coll (+)
A.C.D. = alert 3 mins. (+)
3 mins. enuf (+)
lght off = >3 mins away (c) [faulty?]

A - talks what happened when <3mins. Doesn't weaken the concl.
B - talks about 3 mins not enuf. may be faulty? Keep this one in
C - So, light off does nt necessarily mean planes> 3 mins away (keep it for now)
D & E - No relevance to argument

B -> but enuf to avoid collision. So A.C.D. do avoid coll + option does not attack light off.
Ans C

I use POE method. Correct me if I am wrong. Thanks.

A) Recently, a near collision in which both planes were less than 90 seconds flying distance from each other was averted only by the prompt actions of air traffic controllers.

(B) Some aviation experts warn that in certain cases three minutes may not provide sufficient time for aircrafts to maneuver without causing onboard injuries.

(C) The anti-collision device only signals planes of oncoming directions, not those planes that are flying in parallel.

(D) When two DC-10’s approach each other the red lights on each aircraft do not necessarily turn on simultaneously. -> OFS

(E) The DC-10 is not the only aircraft model to have been installed with the anti-collision device.

Please explain why the OA directly weakens the conclusion.

When we strengthen/weaken an argument, we need to strengthen/weaken the conclusion.
Here the conclusion says "If the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane."

We have to weaken it. That is, we have to establish that red light could be off and still there could be another plane less than three mins flying time away from this plane.

(C) The anti-collision device only signals planes of oncoming directions, not those planes that are flying in parallel.
If anti collision device ignores planes flying parallel, the light could be off but there could be a plane flying parallel to this one which could be less than 3 mins flying time away. It is not necessary that DC-10 is more than 3 mins flying time from any plane. Hence our conclusion is weakened.

Focus on the conclusion.

Official Explanation

The credited answer is (C). Some planes crash because they are oncoming, going in opposite directions headed toward each other, but sometimes planes going in more or less the same direction just drift too close and crash. If the anti-collision device only signals planes of oncoming directions, then it wouldn't prevent crashes of this latter kind. Yes, the anti-collision device would help prevent some categories of crashes, but it still would be possible for two planes, flying more or less parallel, to come dangerously close to one another without the device giving its warning. This points out a significant hole in the aviation analyst's argument.

We don't know what kind of planes were involved here, but only the DC-10's have the anti-collision device, so this scenario could have involved planes that didn't have the device at all. If planes without the device almost crash, that's certainly no reflection on how effective the device is. There is too much uncertainty in this answer. Choice (A) is incorrect.

It's true that onboard injuries would be undesirable, but they're better than a mid-air plane crash! The argument is simply about preventing a mid-air plane crash --- it makes no specific promises about the health and well-being of the passengers. Choice (B) is incorrect.

As long as the anti-collision devices turn on with more than 3 minutes warning for each plane, it doesn't matter whether they turn on at exactly the same time, or are separated by a few seconds. This simply doesn't matter at all. Choice (D) is incorrect.

If other airlines have had this anti-collision device installed, then if anything, that would seem to be a vote of confidence for it, an indication that other companies trust the device and believe that it's effective. This is definitely not a weakener, and could be construed as a mild strengthener. Choice (E) is incorrect.

(A) We don't know what kind of planes were involved here, but only the DC-10's have the anti-collision device, so this scenario could have involved planes that didn't have the device at all. If planes without the device almost crash, that's certainly no reflection on how effective the device is. There is too much uncertainty in this answer. Choice (A) is incorrect.

(B) It's true that onboard injuries would be undesirable, but they're better than a mid-air plane crash! The argument is simply about preventing a mid-air plane crash --- it makes no specific promises about the health and well-being of the passengers. Choice (B) is incorrect.

(C) Some planes crash because they are oncoming, going in opposite directions headed toward each other, but sometimes planes going in more or less the same direction just drift too close and crash. If the anti-collision device only signals planes of oncoming directions, then it wouldn't prevent crashes of this latter kind. Yes, the anti-collision device would help prevent some categories of crashes, but it still would be possible for two planes, flying more or less parallel, to come dangerously close to one another without the device giving its warning. This points out a significant hole in the aviation analyst's argument. Hence, Choice C is correct

(D) As long as the anti-collision devices turn on with more than 3 minutes warning for each plane, it doesn't matter whether they turn on at exactly the same time, or are separated by a few seconds. This simply doesn't matter at all. Choice (D) is incorrect.

(E) If other airlines have had this anti-collision device installed, then if anything, that would seem to be a vote of confidence for it, an indication that other companies trust the device and believe that it's effective. This is definitely not a weakener and could be construed as a mild strengthener. Choice (E) is incorrect.

I like such pure logic auestions.
It is obvious that after reading a passage we have to look for the options, where or this device does not work properly (no red light when necessary), or this device has some nuances like red light goes of, when planes passed each othe, for example, or option C in this case

Facts:
a. To combat human error involved in air traffic control, Miro Jets Inc. has recently installed each of its DC-10 passenger planes with a special anti-collision device.
b. The device alerts the DC-10, via a red light, when another plane is slightly more than three minutes away from a potential collision.
c. Aviation experts at Miro Jet Inc. have determined that three minutes is ample time for a plane to divert its respective flight paths to avoid a collision.

Conclusion -
Therefore, if the red light on the anti-collision device is off, the DC-10 is more than three minutes flying time from any plane.

So, we should look out for an option that would tell us that 3-minutes is not sufficient time to prevent collision or which would undermine the basic definition of "collision".

Option analysis:
(A) Recently, a near collision in which both planes were less than 90 seconds flying distance from each other was averted only by the prompt actions of air traffic controllers.
It does not say whether 3-minutes is an ample time or not.

(B) Some aviation experts warn that in certain cases three minutes may not provide sufficient time for aircrafts to maneuver without causing onboard injuries.
"Certain" cases - too broad.

(C) The anti-collision device only signals planes of oncoming directions, not those planes that are flying in parallel.
Okay hold on

(D) When two DC-10’s approach each other the red lights on each aircraft do not necessarily turn on simultaneously.
even if one turns on the collision can be averted. does not fit our weakening definition

(E) The DC-10 is not the only aircraft model to have been installed with the anti-collision device.
It rather strengthens.