V10-13

Question

Electrician Magazine surveyed 1,000 electricians who took an advanced certification exam. Of these 1,000 candidates 500 passed the exam and 500 failed. The magazine asked the electricians how many hours they had studied for the exam. It was found that those who passed had studied on average 50 hours, and those who failed had studied on average 20 hours. The magazine concluded that the more hours one studies, the more likely they are to pass.
 
Which of the following, if true, would most strengthen the conclusion of the magazine?

A. Some of the electricians in the survey actually studied more than 100 hours.
B. Many of those surveyed thought the exam was unnecessary and did not reflect on their ability as electricians.
C. The electricians in the survey all took the exam shortly after reaching five years of experience as an electrician.
D. Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.
E. Majority of the electricians who failed had college degrees in a variety of fields not related to electrical subjects.

hassi01 · Accepted Answer

I went with D

I understand how C is a good option but I don't understand how D is wrong..

The conclusion is in the last line 'The magazine concluded that the more hours one studies, the more likely he is to pass.'

And option D basically says that many of the electricians who passed completed a course covering similar material to the ones asked in the exam. Shouldn't completing the course mean that those electricians did indeed studied more hours?

Bunuel · Answer

Official Solution:

Electrician Magazine surveyed 1,000 electricians who took an advanced certification exam. Of these 1,000 candidates 500 passed the exam and 500 failed. The magazine asked the electricians how many hours they had studied for the exam. It was found that those who passed had studied on average 50 hours, and those who failed had studied on average 20 hours. The magazine concluded that the more hours one studies, the more likely they are to pass.
 
Which of the following, if true, would most strengthen the conclusion of the magazine?

A. Some of the electricians in the survey actually studied more than 100 hours.
B. Many of those surveyed thought the exam was unnecessary and did not reflect on their ability as electricians.
C. The electricians in the survey all took the exam shortly after reaching five years of experience as an electrician.
D. Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.
E. Majority of the electricians who failed had college degrees in a variety of fields not related to electrical subjects.

The argument concludes that the more hours an electrician studies, the more likely they are to pass the certification exam. If you were asked to weaken this conclusion, you could find some external factor that may have helped one group to do better. However, in this case, we need to strengthen this conclusion and thus do the opposite - rule out external factors that may have interfered and offered an alternative explanation why some electricians passed while others failed. If other factors could have influenced the results, the conclusion about study hours being the primary cause would be weakened. Keep in mind, that the strengthn questions are not explain-type quesitons - they only have to strengthen, not overwhelmingly convince. Thus the evaluation standard is quite low and subtle. 
 
A. "Some electricians studied more than 100 hours" is irrelevant to the argument since the conclusion is based on averages. Even if some electricians studied an exceptionally high number of hours, this does not tell us whether they passed or failed, nor does it provide insight into whether study time was the deciding factor. We can rule this answer choice out as it has insufficient information. 
 
B. "Many surveyed thought the exam was unnecessary" does not affect the conclusion. The electricians&rsquo; opinions about the exam are irrelevant to whether study time affects their likelihood of passing.
 
C. (Correct Answer) This option strengthens the argument because it eliminates a potential alternative explanation — differences in experience. If all electricians had the same level of experience when they took the exam, it becomes more likely that the difference in study hours, rather than varying levels of experience, influenced their performance. By ruling out experience as a factor, this option increases the likelihood that the number of study hours is the key factor in passing the exam. This option does not guarantee that the study hours were the sole and only contributor, but it moves the argument in the right direction and strengthens it. 
 
D. "Many electricians who passed completed a course in electronics" weakens the conclusion because it introduces another factor—prior coursework—that could explain why those electricians passed. If those who passed had extra knowledge from the course, their success could be due to that advantage rather than the amount of time spent studying for the exam.
 
E. Similarly, this option weakens the conclusion by suggesting that electricians who failed had degrees in unrelated fields. This implies that their failure may have been due to a lack of relevant knowledge, rather than the number of study hours, introducing an alternative explanation.
 
Thus, option C strengthens the argument by ruling out a significant alternative factor—experience—and supporting the conclusion that study hours were a decisive factor in passing the exam.

Answer: C

Bunuel · Answer

The question or/and solution has been revised and edited. Thank you  sayantanc2k  !!!

Rickooreo · Answer

KarishmaB   gmatophobia   sayantanc2k

Can you please help me understand why option D is wrong.
Option D - Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.

D basically says that many of the electricians who passed completed a course covering similar material to the ones asked in the exam. Shouldn't completing the course mean that those electricians did indeed studied more hours?

gmatophobia · Answer

While experts weigh in their opinion, sharing my two cents - The conclusion of the argument is - more hours one studies, the more likely he is to pass. . So the magazine / author believes that extras hours that the electricians put was the only reason and there was no other variable(s) at play. We have to strengthen the argument. So in someway, we have to lend support to the conclusion in the line of assumption made. Option D - infact weakens as it presents us with an alternate reason, that might have been at play and helped the electricians pass the advanced certification exam. That is the option presents us with a reason that goes against the conclusion that the result was not because of more number of hours that the electricians had put in but because of the familiarity of the material that the electricians had. Now, I understand your thoughts are around the fact, that the electricians might have put some additional hours as a part of the initial course work, but that's something we are concocting to support our hypothesis. It's not given in the passage, so its not right to assume one. The electricians might have cheated in the course work and have genuinely put in more hours to pass the advance certification exam.

In CR one should stick to the details given in the passage. Reminds me of a statement GMATNinja always emphasis in his CR sessions- " Is it their words or my words " Clearly in here it is my words if I assume that merely because the electricians have taken an additional course, that means they have put in more efforts studying for that course. Hope that helps.

KarishmaB · Answer

1000 people took an exam. 500 passed. 500 failed.
It was found that the 500 who passed had studied on avg 50 hrs while 500 who failed had studied on avg 20 hrs.

Conclusion: The more hours you put in, the more likely you are to pass.

We need to strengthen this. Note that there could be many reasons why the 500 who passed actually did pass. We only checked for one characteristic and that was the number of hours they put in. What if the 500 who passed had an avg experience of 10 yrs compared with an avg experience of 2 yrs of those who did not pass? What if the 500 who passed had already acquired some related certifications and hence knew the material much better? What if the 500 who passed had college degrees in the field of Electricals? Any one of these could be the differentiating factor. We only checked for one factor (number of hrs) and concluded based on that. We can strengthen that number of hours was responsible by showing that other possible factors were not responsible.

C. The electricians in the survey all took the exam shortly after reaching five years of experience as an electrician.
Option (C) says that they had the same experience. So it says that a difference in their experience level was not responsible. So it increases the likelihood that 'number of hrs put in' was the factor responsible. Note that it just increases the probability but that is all we need from a strengthener - an increased probability.

A. Some of the electricians in the survey actually studied more than 100 hours.

We are talking about averages in our argument. Even if some people studied a lot (we don't know whether they passed or failed), it doesn't impact our conclusion.

B. Many of those surveyed thought the exam was unnecessary and did not reflect on their ability as electricians.

What they thought about the importance of the exam is irrelevant.

D. Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.

If anything, it weakens the conclusion. It links 'passing' with another factor - 'other courses in electronics.' But it doesn't tell us that those who failed had not completed such courses so the information is limited. In any case, we can be sure that it doesn't strengthen.

E. Majority of the electricians who failed had college degrees in a variety of fields not related to electrical subjects.

Same as option (D). If anything, it weakens the conclusion. It links 'failing' with another factor - non electrical degree. But it doesn't say that those who passed had electrical degrees. But in any case, we know that it doesn't strengthen.

Answer (C)

SSgmat2024 · Answer

I think this the explanation isn't clear enough, please elaborate.

bb · Answer

Thanks for the question. I have updated the explanation in the tests and also in the second post of the topic.

sssdd1234 · Answer

I think this is a  high-quality  question and I agree with explanation.

Aarti0701 · Answer

Even if the 3rd option is right, intelligence can play a role in determining the passing electrician rather than study hours, However option D may be right as they did study extra through different course which other might not have studied. so studying extra hour became the factor

bb · Answer

This is not a question about what is right but what strengthens the conclusion.

Option D, while could be a real situation, actually weakens the conclusion and is therefore the incorrect answer choice. 
Option E, similarly weakens the conclusion.

APram · Answer

I like the solution - it’s helpful.

Abhishek_Relan · Answer

I like the solution - it’s helpful.

Sushi_545 · Answer

Hi  Bunuel ,  bb , @ KarishmaB ,  @  gmatophobia   ,@  sayantanc2k
C an anyone help here

If we assume Candidate who have 5 year work exp passed the exam and with 3 year work ex have not. Then isnt this example going against like having more work ex they are studying more hours?

A-> 5hrs -> work ex->5yrs

B-> 3 hrs -> work ex-> 2yr

thats why i have choosen D

here work ex is actually making the person to study longer. how would you justify this?

bb · Answer

D) weakens the conclusion. I do have to admit that I am not following your example here with 4 hours and 5 years or 2 years. The question does not talk about years... so I am not sure why the years are brought up or relevant in this example

D tells us that they have taken a special course which means that the hours are not helping but the course is and our conclusion is that the hours should be helping. Let me know what I am missing from your example above. The years of work experience and everything else does not matter, we are aiming to strengthen the conclusion that hours of studying is the only differentiator.

Sushi_545 · Answer

Hi bb,

I meant to say if we assume choice D to be correct "  Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam." it means electricians have already spent some hours say "X" hours learning about the course and now the argument is saying "  It was found that those who passed had studied on average 50 hours, and those who failed had studied on average 20 hours." 
so amount of hours spent by those who passed :- 50+x
Those who failed:- 20

So i thought it to be supporting the conclusion as 50+x>20, right?

bb · Answer

No.

The conclusion is that the studying for 50 hours is ALONE what's responsible for passing the exam.

In D) the answer choice introduces ANOTHER variable which is not covered in the text. This variable creates uncertainty and WEAKENS the conclusion, making us wonder whether people passed due to studying for 50 hours or perhaps studying was completely useless and the only reason they passed was that they took this additional course and they just happen to have studied 50 hours or maybe studying was only partially responsible for improvement. Whichever way you look, even if only 1%, it still weakens.

Sushi_545 · Answer

Yeah much better position now. I am glad to be satisfied with this.

srik410 · Answer

I like the solution - it’s helpful. Nice subtle question. FYI, Chatgpt 4o(general purpose model) got this wrong, but o3 model(advanced reasoning), got this right with 90% confidence. Shows that definitely there is something to learn from here.

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