Critical Reasoning

Since the deregulation of airlines, delays at the nation's increasingly busy airports have increased by 25 percent.
To combat this problem, more of the takeoff and landing slots at the busiest airports must be allocated to
commercial airlines. Which of the following, if true, casts the most doubt on the effectiveness of the
solution proposed above?
A. The major causes of delays at the nation's busiest airports are bad weather and overtaxed air traffic control
equipment.
B. Since airline deregulation began, the number of airplanes in operation has increased by 25 percent.
C. Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial
airlines.
D. After a small midwestern airport doubled its allocation of takeoff and landing slots, the number of delays that
were reported decreased by 50 percent.
E. Since deregulation the average length of delay at the nation's busiest airports has doubled.


IMO - c , while OA -a how????

varun289 wrote:Since the deregulation of airlines, delays at the nation's increasingly busy airports have increased by 25 percent.
To combat this problem, more of the takeoff and landing slots at the busiest airports must be allocated to
commercial airlines. Which of the following, if true, casts the most doubt on the effectiveness of the
solution proposed above?
A. The major causes of delays at the nation's busiest airports are bad weather and overtaxed air traffic control
equipment.
B. Since airline deregulation began, the number of airplanes in operation has increased by 25 percent.
C. Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial
airlines.
D. After a small midwestern airport doubled its allocation of takeoff and landing slots, the number of delays that
were reported decreased by 50 percent.
E. Since deregulation the average length of delay at the nation's busiest airports has doubled.


IMO - c , while OA -a how????

Due to deregulation, delay increased by 25%. On increasing commercial slots, the delay should decrease. However, if the delays are not due to lack of commercial airlines at all, they will not decrease and hence cast a serious doubt on the solution provided.

Deregulation of Airport => Delays increased by 25 %.
Allocate more landing-takeoff slots to commercial planes=>reduction in time consumed during takeoff and landing,

To weaken this we can say that delay is not due to planes or any mechanical arrangement, but due to other natural factor.

Option (A) is correct answer.

If you have a plan question such as this one, you can weaken the effectiveness of the plan if you show that the plan is not caused by the cause that the question assumes.

For example, this question makes the assumption that the cause of the delays is a lack of spots for commercial airlines. What if instead of a lack of spots the problem is in another area - such as weather, or delays with baggage or passenger loading? The increased spots will not combat this...

You mention choice C - here is my question for you - Is over 60% of the spots reserved for commercial airlines a lot of spots? Is it not that many? How many would you expect? Do you see the problem here? This is information that may or may not actually weaken the plan - depending on information that you do not have....

The answer is very doubtful. There must be an explanation why before de-regulation there was not much delays and after deregulation event there is an increase in delays.
The option A is very general. Did the climate change after the deregulation event ?

What is the source ?

David@VeritasPrep wrote:If you have a plan question such as this one, you can weaken the effectiveness of the plan if you show that the plan is not caused by the cause that the question assumes.

For example, this question makes the assumption that the cause of the delays is a lack of spots for commercial airlines. What if instead of a lack of spots the problem is in another area - such as weather, or delays with baggage or passenger loading? The increased spots will not combat this...

You mention choice C - here is my question for you - Is over 60% of the spots reserved for commercial airlines a lot of spots? Is it not that many? How many would you expect? Do you see the problem here? This is information that may or may not actually weaken the plan - depending on information that you do not have....

This is an Official GMAT question!

It is question 16 from the Verbal Review 2nd edition.

Remember that you must assume that ALL answer choices are true. It says it there in the question, "Which of the following, if true, casts the most doubt..."

So if it is true that the delays are weather and traffic control, well these extra takeoff and landing slots would not help with those problems.

Thanks a lot David. Your responses are very clear.

vigneshahob wrote:The answer is very doubtful. There must be an explanation why before de-regulation there was not much delays and after deregulation event there is an increase in delays.
The option A is very general. Did the climate change after the deregulation event ?

What is the source ?

David@VeritasPrep wrote:If you have a plan question such as this one, you can weaken the effectiveness of the plan if you show that the plan is not caused by the cause that the question assumes.

For example, this question makes the assumption that the cause of the delays is a lack of spots for commercial airlines. What if instead of a lack of spots the problem is in another area - such as weather, or delays with baggage or passenger loading? The increased spots will not combat this...

You mention choice C - here is my question for you - Is over 60% of the spots reserved for commercial airlines a lot of spots? Is it not that many? How many would you expect? Do you see the problem here? This is information that may or may not actually weaken the plan - depending on information that you do not have....

David@VeritasPrep wrote: You mention choice C - here is my question for you - Is over 60% of the spots reserved for commercial airlines a lot of spots? Is it not that many? How many would you expect? Do you see the problem here? This is information that may or may not actually weaken the plan - depending on information that you do not have....

Hi Verbal Experts (@VeritasPrep/others),
I'm still confused with choice C.

In a WEAKEN (or a STRENGTHEN) CR, I think, the correct choice will be a "MIGHT BE TRUE" option -- it doesn't need to be MUST BE TRUE. Right ?

Then how the choice C is INCORRECT, although it's a "MIGHT BE TRUE" option ?

Please help!

RBBmba@2014 wrote:

David@VeritasPrep wrote: You mention choice C - here is my question for you - Is over 60% of the spots reserved for commercial airlines a lot of spots? Is it not that many? How many would you expect? Do you see the problem here? This is information that may or may not actually weaken the plan - depending on information that you do not have....

Hi Verbal Experts (@VeritasPrep/others),
I'm still confused with choice C.

In a WEAKEN (or a STRENGTHEN) CR, I think, the correct choice will be a "MIGHT BE TRUE" option -- it doesn't need to be MUST BE TRUE. Right ?

Then how the choice C is INCORRECT, although it's a "MIGHT BE TRUE" option ?

Please help!

I received a PM asking about this one.

You're right that when we get a weaken question, we're not weighing the likelihood that a given answer choice is true, but rather, attempting to determine what impact the answer choice, if true, will have on a plan or conclusion.

In this case we're trying to weaken the conclusion that allocating more takeoff and landing space to commercial airlines will help mitigate delays.

Answer choice C: Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial
airlines. This doesn't weaken the conclusion. If, at the time the airports are dealing with delays, 65% of the runways are allocated to commercial airlines, bumping that number up to, say, 90%, could very well address the problem if the issue is a commercial airline bottleneck. That 60% figure is totally arbitrary. But if the issue is bad weather (answer choice A) no amount of increased runway space is going to do anything to get people in the air any faster.

DavidG@VeritasPrep wrote:You're right that when we get a weaken question, we're not weighing the likelihood that a given answer choice is true, but rather, attempting to determine what impact the answer choice, if true, will have on a plan or conclusion.

In this case we're trying to weaken the conclusion that allocating more takeoff and landing space to commercial airlines will help mitigate delays.

Answer choice C: Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial
airlines. This doesn't weaken the conclusion. If, at the time the airports are dealing with delays, 65% of the runways are allocated to commercial airlines, bumping that number up to, say, 90%, could very well address the problem if the issue is a commercial airline bottleneck. That 60% figure is totally arbitrary. But if the issue is bad weather (answer choice A) no amount of increased runway space is going to do anything to get people in the air any faster.

There goes my doubt - Over 60 percent could also mean say, 92% of the runways are allocated to commercial airlines. Right ?

So, in that case bumping that number up to, say, 97%, would NOT likely address the problem if the issue is a commercial airline bottleneck. Thus the CONCLUSION is WEAKENED.

Bottom-line: are we discarding the Option C because in one hand it seems to STRENGTHEN the CONCLUSION, on the other hand it seems to WEAKEN the CONCLUSION.

RBBmba@2014 wrote:

DavidG@VeritasPrep wrote:You're right that when we get a weaken question, we're not weighing the likelihood that a given answer choice is true, but rather, attempting to determine what impact the answer choice, if true, will have on a plan or conclusion.

In this case we're trying to weaken the conclusion that allocating more takeoff and landing space to commercial airlines will help mitigate delays.

Answer choice C: Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial
airlines. This doesn't weaken the conclusion. If, at the time the airports are dealing with delays, 65% of the runways are allocated to commercial airlines, bumping that number up to, say, 90%, could very well address the problem if the issue is a commercial airline bottleneck. That 60% figure is totally arbitrary. But if the issue is bad weather (answer choice A) no amount of increased runway space is going to do anything to get people in the air any faster.

Here goes my doubt - Over 60 percent could also mean say, 92% of the runways are allocated to commercial airlines. Right ?

So, in that case bumping that number up to, say, 97%, would NOT likely address the problem if the issue is a commercial airline bottleneck. Thus the CONCLUSION is WEAKENED.

Bottom-line: are we discarding the Option C because in one hand it seems to STRENGTHEN the CONCLUSION, on the other hand it seems to WEAKEN the CONCLUSION.

Exactly. Anytime you have a weaken question (or a strengthen question, for that matter), an answer choice that is so open-ended that it could either weaken or strengthen the conclusion can't possibly be correct.

In GMAT CR, if we've phrases such as Over 60 percent, then should we consider BOTH the higher and lower-end ranges ALWAYS ?
I mean, should we consider BOTH say,65% and 97% every time in order to choose the OA (as we did in the above case to analyse Answer choice C)?

RBBmba@2014 wrote:In GMAT CR, if we've phrases such as Over 60 percent, then should we consider BOTH the higher and lower-end ranges ALWAYS ?
I mean, should we consider BOTH say,65% and 97% every time in order to choose the OA (as we did in the above case to analyse Answer choice C)?

Generally speaking, I think that's a reasonable practice, though it isn't hard to come up with a hypothetical in which such thinking wouldn't be necessary. (Say the conclusion were something like, at least 80% of the population in Community x will purchase product y. If we wanted to weaken this conclusion, an answer choice that stipulated over 25% of the population in Community x has been diagnosed with a fatal allergy to product y, wouldn't require this type of analysis, because if 26% of the population won't consider purchasing the product, we already know that the conclusion is demonstrably weakened, as only 74% of the population can use product y without the risk of death! No reason to then consider the possibility that 97% of the population has the allergy, though the conclusion is obviously weakened in this case as well.)

@Dave - Offhand, do you've have any Official example(s) representing the LOGIC you mentioned above ?