Investigators concluded that human failure was not responsible for the

C for me as well. Without C, you cannot safely reach the conclusion that the increase in reports is due to more stringent reporting requirements

Very interesting question
IMO C

Investigators concluded that human failure was not responsible for the fatal airplane crash last August, and since that time new and more stringent rules for identifying and reporting mechanical problems have been in effect. That accounts for the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August.

Which one of the following is an assumption underlying the argument in the passage?

(A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems --> out of scope
(B) Mechanical problems in airplanes have increased dramatically since last August --> this is a weaken, not an assumption. Because this give an alternative for the increase of reports of mechanical problems since last August, besides the operation of rules for mechanical problems reporting
(C) Mechanical problems in airplanes have not increased by 50 percent since last August -->best answer. You can use the Assumption negative technique in Bible critical Power score: Mechanical problems in airplanes have increased by 50 percent since last August--> this turns out to be a weaken to the argument, so this is the best choice
(D) Airlines are less reluctant to report mechanical problems than they previously were --> this seems alright, but not as strong as (C). The reluctance is just a weak and abstract reason to decide whether to report a mechanical problem. But because the frequency increase dramatically, 50%, so the reluctance seems to play no significant role
(E) Mechanical problems in airplanes have become easier to detect since last August --> weaken

IMO C

Investigators concluded that human failure was not responsible for the fatal airplane crash last August, and since that time new and more stringent rules for identifying and reporting mechanical problems have been in effect. That accounts for the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August.
Which one of the following is an assumption underlying the argument in the passage?
(A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems --> this is not about the result of increase mechanical reports, but about the cause of them
(B) Mechanical problems in airplanes have increased dramatically since last August -->weaken. More mechanical problems-->more reports (not because of more rules)
(C) Mechanical problems in airplanes have not increased by 50 percent since last August -->negating this: Mechanical problems in airplanes have increased by 50 percent since last August -->weaken like (B). So, the best
(D) Airlines are less reluctant to report mechanical problems than they previously were -->weaken. Because airlines are now likely to report mechanical problems than they were before, this accounts for the fact that mechanical reports increase (not because of more rules)
(E) Mechanical problems in airplanes have become easier to detect since last August -->another weaken. Analyzing like (B) & (D)

Investigators concluded that human failure was not responsible for the fatal airplane crash last August, and since that time new and more stringent rules for identifying and reporting mechanical problems have been in effect. That accounts for the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August.
Which one of the following is an assumption underlying the argument in the passage?
(A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems.
(B) Mechanical problems in airplanes have increased dramatically since last August.
(C) Mechanical problems in airplanes have not increased by 50 percent since last August.
(D) Airlines are less reluctant to report mechanical problems than they previously were.
(E) Mechanical problems in airplanes have become easier to detect since last August.

Anwser: C
It says "Mechanical problems in airplanes have not increased by 50 percent since last August."..The conclusion is the reports were increased by 50% which means already existing problems were reported rather than new problems.

Its C for me...If the reason is not human error then it should be mechanical problem...To make it true, the amount of mechanical problems today should not be much more than that present earlier...C brings it out clearly...

C


In short the arguments says: We have more stringent rules for identifying problems => problem reports increased by 50%.

But maybe the increase in reporting is not based on improved procedures? Maybe reason is the overall increase in number of problems?

Argument implies that the number of problems was the same and number of reports increased solely because of new rules. If this assumption does not hold then the argument is clearly faulty.

So for argument to be true the assumption (C) must hold.

Its C only,

D states that now airline are more eager to report => increase in the reports is because of their eagerness not because of the rules.

Ans is C
Premise :50% increase in reporting airplane mechanical problems
conc: Human failure not responsible
Assp:Mechanical problems in airplanes have not increased by 50 percent since last August

Can some one explain how can it be 'C' ? , I felt confused at 'if reports were increased by 50%, how can we conclude that those 50% reports doesn't constitute to 50% of mechanical problems ?'. Here I assume 50% mechanical problems as the problems that are newly raised. Thankyou

Hi
I am not expert, but expert can comment on my reasoning

Because of stringent rules for identifying and reporting mechanical problems are in effect, reports of airplane mechanical problems have increased in frequency by 50 percent since last August.
Eg. before stringent rules mechanical problems reported were 50 , but actually there were 75 problems. So 25 were not reported.
After stringent rules, mechanical problems reported are 75 and in reality also 75 problems are there.
This means reports of airplane mechanical problems increased in frequency by 50 percent but actual problems have not increased. this is choice C which supports that only report frequency has increased , not actual problems count are same.

This assumption is needed because author specifically says --- more stringent rules for identifying and reporting mechanical probbeen ilems have n effect. That accounts for the fact that reports -----
If actual problems itself are increasing then we cant attribute increase in reporting to stringent rules.
We have to show, problems are all same only more stringent rules have helped to identify the problem.

GMATNinja
could you explain this Q ?