#Argument Family, #Flaw in Logic, #Averages

Question


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?

(Because of copyrights, the complete official question is not copied here. You can access the question here: GMAT Club)

Difficulty: Medium

Accuracy: 71%

Based on: 7111 sessions

Solution


The Story

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.

Question Stem

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

Prediction:
In line with the above gap analysis.

Answer choice analysis


Answer Choice: A

Incorrect

Selected by: 6%

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.


Answer Choice: B

Incorrect

Selected by: 8%

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.


Answer Choice: C

Incorrect

Selected by: 5%

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.


Answer Choice: D

Correct

Selected by: 71%

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.


Answer Choice: E

Incorrect

Selected by: 11%

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.

Additional Notes


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 that we can.


The accuracy data is from GMAT Club and might have changed since the time of publishing this solution. If you have any doubts regarding any part of this solution, please feel free to ask in the comments section.

You can go through detailed solutions to many other official GMAT questions here.

Anish Passi

GMAT Coach

With over a decade of GMAT training experience, top 1 percentile scores on the CAT and GMAT, and a passion for teaching, I’d like to believe I am quite qualified to be a GMAT coach. GMAT is learnable, and I help students master the GMAT through a process-oriented approach based on logic and common sense. I offer private tutoring and live-online classroom courses. My sessions are often sprinkled with real-world examples, references to movies, and jokes that only I find funny. You’ve been warned 🙂

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