Debater: The average amount of overtime per month worked by

Manufacturing division of HC (say has 100 people)- Avg overtime per month = 14 hrs

Manufacturing division has most employees (so say total number of HC employees is 110)
Avg overtime per month for all employees stays steady month to month (say it stays between 13.5 to 15 hrs per month)

Conclusion: Each month, most employees of HC almost certainly work at least some overtime.

What is the flaw here? It talks about average overtime and then concludes the average holds for each member. It is certainly possible that of the 100 people in manufacturing division, 20 people work 70 hrs overtime per month while 80 people work no overtime. Can I say that most employees work at least some overtime? No! Of the total 110 people, 80 work no overtime at all!

This is exactly what (D) says:
(D) It overlooks the possibility that even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all.

Answer (D)

(A) It takes for granted that the manufacturing division is a typical division of the corporation with regard to the average amount of overtime its employees work each month.

It doesn't. It is concluding about each employee.

(B) It takes for granted that if a certain average of amount of overtime is worked each month by each employee of the Haglut Corporation, then approximately the same amount of overtime must be worked each month by each employee of the manufacturing division.

Again, it doesn't. Avg of HC and avg of Manufacturing division in HC could be a bit different.

(C) It confuses a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow with a claim that would follow from the argument's conclusion only with a high degree of probability.

This is just given to confuse the heck out of you! My first thought was "there is neither a claim given from which the conclusion can follow, nor is there a claim which follows from the conclusion". The argument gives verifiable data, but claims nothing other than the conclusion from the data. The only claim is the conclusion. Hence I moved on to the next option.
A cursory glance might make you think that what they are concluding has a high degree of possibility but the conclusion gives is as almost a certainty and well, that is the problem. But note that even then, you should know that what the conclusion concludes does not have a high degree of probability. We have no grounds to believe that every employee would probably work some overtime at least. It is very much possible that very few people put in a lot of overtime while other don't. We don't know the requirements of the industry.

(E) It overlooks the possibility that even if most employees of the corporation work some overtime each month, anyone corporate employee may, in some months, work no overtime.

The conclusion is about most employees, not all employees so this is not the flaw.

D because we care about a group that is the major part of the company employees that work overtime.

Though question for me

How can we consider Option D as correct if its only talking about "some group" but not the whole organization? Would be great if somebody can explain.

Above statement is a generic statement not specific to that organization. This statement is applicable for manufacturing group where if on average there is overtime of 14 hrs/ month doesnt mean that everyone in the manufacturing group is doing the overtime.

Thanks,
Sankalp
­

Debater: The average amount of overtime per month worked by an employee in the manufacturing division of the Haglut Corporation is 14 hours. Most employees of the Haglut Corporation work in the manufacturing division. Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime.

The debater's argument is most vulnerable to criticism on which of these grounds?

Average No Overtime for per months =14 hrs/month = (Total sum of hrs of only those employees who actually put extra overtime hours in a year )/12 * Total no of employees in the Org , this include the sleeping one also

Also from question , there is no fluctuation in per month , so the variable parameters in above equation are , employee who actually work overtime and and rest others

suppose total 10 employees , 7 belongs to manufacturing division (As most belongs to it ) whose overtime is 14 hrs and now from the second gp we can have 1 person putting 42 hrs overtime and rest two sleeping but still giving the avg of 14hrs /month (42/3)

The same is justified by the option D ,
My Funda Making CR more mathematical and Logical

A real tough one! I felt the answer choices were tougher to comprehend than the argument. I felt nice while going through the argument and i was through to the answer choices in ~30 secs. But soon was entangled in the choices and lost all the confidence gained from the argument

I lost about >1 min on choice C alone (had to revisit the passage once and reread the choice multiple times).
I felt choice C was strategically placed before the correct answer. Does GMAT play here too?

How do we deal with this kinda situation? Is there a way to know if the choice that seems the toughest to comprehend is not the correct answer?

Btw, i still have little clue about what choice C meant

It confuses a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow with a claim that would follow from the argument's conclusion only with a high degree of probability.

It confuses a
claim ------100%------> argument's conclusion
with a
claim <------high probability------ argument's conclusion

To put it another way, the third option is trying to say that the argument is vulnerable to the criticism that it (the argument) fails to differentiate between
a claim that would definitely lead to the argument's conclusion
and
a claim that the argument's conclusion would lead to (with a high degree of probability).

Super easy D

Manufacturing works requires 14 hours of overtime in jan, feb mar, april, may june...etc etc (their average overtime stays constant=14 hr per employee per month. But in january and feb engine specialist work overtime because more engines are produced, In march and april, glass cutters and painters work overtime, in june and july, body makers do overtime) and then we can also have that tyre fitters in the same manufacturing division that never work over time , there overtime is also constant 0 hour per employee per month)

Option D acounts for all such cases
D) even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all.

Debater: The average amount of overtime per month worked by an employee in the manufacturing division of the Haglut Corporation is 14 hours. Most employees of the Haglut Corporation work in the manufacturing division. Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime.

100 employees
month -Jan

1 employee of Manufacturing division = 14*12

Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. :- so let say if a employee work 1 hour overtime in a month most of the time it is 1 or nearby.

From this : each month, most employees of the Haglut Corporation almost certainly work at least some overtime.

There is a huge leap from one employee to every other employee.

The debater's argument is most vulnerable to criticism on which of these grounds?



(B) It takes for granted that if a certain average of amount of overtime is worked each month by each employee of the Haglut Corporation, then approximately the same amount of overtime must be worked each month by each employee of the manufacturing division.

why not B????

(C) It confuses a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow with a claim that would follow from the argument's conclusion only with a high degree of probability.

(D) It overlooks the possibility that even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all.

(E) It overlooks the possibility that even if most employees of the corporation work some overtime each month, anyone corporate employee may, in some months, work no overtime. :- it actually restate the conclusion

Debater: The average amount of overtime per month worked by an employee in the manufacturing division of the Haglut Corporation is 14 hours. Most employees of the Haglut Corporation work in the manufacturing division. Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime.

Type- Weaken
Boil it down -Average overtime per month in manufacturing is 14 hours . Most of employees work in Manufacturing division .
Therefore , each month, most employees of the Haglut Corporation almost certainly work at least some overtime.
Standard deviation in such situations provide a better picture .

Pre- Thinking - Average do not give proper picture of the distribution of the overtime hours among employees .
Hence , our conclusion is vulnerable to criticism that very few employees may be doing the bulk of overtime work


(D) It overlooks the possibility that even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all.

GMATNinja VeritasKarishma AjiteshArun egmat

Does this line play anyb role in the question. I am not getting it. Please help.

You can safely ignore it.

It helps slightly to reinforce the each month part of the conclusion (Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime). The correct option however, doesn't need this statement. It attacks something more fundamental: if many employees work no overtime, it becomes much harder for us to say that most employees almost certainly work some overtime each month. But if the individual figures are just relatively stable (that is, they don't fluctuate), we don't know whether most are non-zero or not.

Dear AjiteshArun,

I have one follow-up question on this very very confusing answer choice:

Is my understanding correct?

a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow
= the claim is a premise on which the conclusion depends

a claim that would follow from the argument's conclusion only with a high degree of probability
= the claim is an inference from the conclusion

Thank you for your great explanation as always

Hi varotkorn,

You're on the right track. One quick change we could make here is to the depends. "Necessarily follow" is closer to sufficient than it is to necessary. For example:

Bad news day → Twitter meltdown

Let's say that a BND always leads to a TM. That is, a TM necessarily follows a BND. This, in itself, does not mean that a BND is necessary for a TM to happen. A TM could happen in the complete absence of a BND as well.

Debater: The average amount of overtime per month worked by an employee in the manufacturing division of the Haglut Corporation is 14 hours. – The average overtime per month worked by an employee in a particular division of a company was 14 hours.

Most employees of the Haglut Corporation work in the manufacturing division. – More than half of the company’s employees work in that division.

Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. – The average overtime per month of a company employee doesn’t fluctuate much. (I notice that the first statement talks about the average overtime worked by a manufacturing division employee, whereas this one talks about the average overtime by any employee in the company. So the average overtime worked by an employee of a particular division is given, and we’re told that an employee of the company (any division), on average, worked roughly the same amount of overtime every month.)

Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime. – The author concludes that most employees of the company work overtime each month.

Author’s logic:

Mainpoint: Most employees of the company work at least some overtime per month.

Why?

Because,

1. The manufacturing division employs most of the employees of the company
2. That division’s employee, on average, works a significant amount of overtime every month (14 hours of overtime per month)
3. And, the average amount of overtime worked by the people in the company does not fluctuate much

Gap(s) in logic:

1. Maybe a fraction of employees in the manufacturing division work overtime, but they work insane hours of overtime, bringing the average for the entire division to 14 hours per month. Thus, it isn’t necessary that every employee of the manufacturing division works overtime. For that matter, it isn’t even necessary that most of the manufacturing division employees work overtime.
2. Maybe the average overtime figure for the entire company is very low, and none of the employees in other divisions work any overtime at all.

The debater’s argument is most vulnerable to criticism on which of these grounds?

Framework
Essentially, what’s a flaw in the logic of the debater’s argument?
I have figured out two gaps (flaws) above. There, of course, could be more too.



A. It takes for granted that the manufacturing division is a typical division of the corporation with regard to the average amount of overtime its employees work each month.
Incorrect.The option states that the author takes for granted that the manufacturing division is a typical division of the corporation with regard to average overtime.
Does the argument believe that a typical division of the company works close to 14 hours of overtime per month – just the way the manufacturing division does?
No.
The conclusion isn’t that the company’s overall average overtime is close to 14 hours per month. In the conclusion, the author claims that most employees work at least some overtime. The overtime worked by the other divisions need not be close to the overtime of the manufacturing division for the argument to make sense. This isn’t a flaw in the argument.

B.It takes for granted that if a certain average of amount of overtime is worked each month by each employee of the Haglut Corporation, then approximately the same amount of overtime must be worked each month by each employee of the manufacturing division.
Incorrect.What’s taken for granted according to this answer choice? That if each employee works a certain average amount of overtime, then each employee of the manufacturing division also works approximately the same amount of overtime.

The argument doesn’t do that. We are given in the passage the average overtime of a manufacturing division employee – 14 hours. This figure is not based on the overtime worked by every employee of the company. In fact, the amount of average overtime worked by each employee of the company is not even mentioned. The debater’s conclusion cannot be criticised on this basis.

C. It confuses a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow with a claim that would follow from the argument's conclusion only with a high degree of probability.
Incorrect. What does the statement mean?

The argument confuses one claim with another.

Let’s say the claims are Claim 1 and Claim 2.

Claim 1:
‘a claim from which the argument’s conclusion […] would necessarily follow’
Claim 1 → conclusion (necessarily)

Claim 2:
‘a claim that would follow from the argument’s conclusion only with a high degree of probability’
Conclusion → Claim 2 (probably)

Does the argument confuse any such claims? In fact, does the argument even have two such claims to confuse? There certainly is no claim that follows the argument’s conclusion. So, the question of confusing such claims doesn’t arise.

The key to understanding why this answer choice is incorrect lies in reading the answer choice patiently and precisely to understand what the statement means. Once we do that, it becomes easier to note that the argument does not have any such confusion.

D. It overlooks the possibility that even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all.
Correct.This option is in the line with the first gap discussed above.
The debater does make this mistake. It is possible that many (even most) employees in the manufacturing division work no overtime at all. And so, the conclusion is flawed.

In other words, even if a certain amount of overtime (14 hours) is worked by the members of some group (manufacturing division), many members of that group may work no overtime at all, and thus, the conclusion that most employees of the company almost certainly work at least some overtime need not be true.

This is a possibility the argument overlooks.

E. It overlooks the possibility that even if most employees of the corporation work some overtime each month, any one corporate employee may, in some months, work no overtime.
Incorrect. What possibility? That even if most employees of the corporation work some overtime each month, any one corporate employee may, in some months, work no overtime.

Does the argument overlook this possibility?

The argument deals with averages. The author concludes that most employees work at least some overtime. The conclusion could very well be made even if some employees (could be corporate employees) work no overtime. The author does not overlook this possibility.


Although very few test-takers choose option C as the correct answer on GMAT Club, I find that the reasoning is incorrect for a much higher proportion. And the typical reason is that many students do not even understand what the statement is saying.
Even if you got the answer correct, it makes sense to spend time to understand and confirm your reasons behind eliminating all incorrect answers. The idea is to extract as much juice (learning) from each question as you can.

Understanding the argument - 
­Debater: The average amount of overtime per month worked by an employee in the manufacturing division of the Haglut Corporation is 14 hours. - Fact. Background info. 
Most employees of the Haglut Corporation work in the manufacturing division. - Fact. Most means >= 51%
Furthermore, the average amount of overtime per month worked by any employee in the company generally does not fluctuate much from month to month. - Fact. 
Therefore, each month, most employees of the Haglut Corporation almost certainly work at least some overtime. - Conclusion. >=51% work at least some overtime. 

The debater's argument is most vulnerable to criticism on which of these grounds?

Option Elimination - 

(A) It takes for granted that the manufacturing division is a typical division of the corporation with regard to the average amount of overtime its employees work each month. - Yes, this is a typical division because it has >=51% of the employees. This is not the flaw. Distortion. 

(B) It takes for granted that if a certain average of amount of overtime is worked each month by each employee of the Haglut Corporation, then approximately the same amount of overtime must be worked each month by each employee of the manufacturing division. - opposite connection. Distortion. 

(C) It confuses a claim from which the argument's conclusion about the Haglut Corporation would necessarily follow with a claim that would follow from the argument's conclusion only with a high degree of probability. - First, there is no claim that the author has made to arrive at the conclusion. He has just stated facts. Moreover, there is no claim driven from the conclusion. Out of scope. This option uses all the jargon and familiar words to create a trap.

(D) It overlooks the possibility that even if, on average, a certain amount of overtime is worked by the members of some group, many members of that group may work no overtime at all. - Yes. True. If 30% or 40% of the employees do 120 hours per month (double shift), then 49% (other than manufacturing) + 21 to 11% of manufacturing employees = 60 to 70% of the employees don't have overtime at all. So we can't conclude ">=51% work at least some overtime. "

(E) It overlooks the possibility that even if most employees of the corporation work some overtime each month, any one corporate employee may, in some months, work no overtime. - The conclusion has already been taken into account when the author concludes, ">=51% work at least some overtime." Say 52% work at least some overtime. So, the author already takes into account that 48% didn't work overtime at all. The one that this option states is part of this 48%. Distortion.