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15 Dec 2025, 09:00
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
63% (02:00) correct
37%
(02:04)
wrong
based on 402
sessions
History
Date
Time
Result
Not Attempted Yet
Last year, 10 percent of doctors younger than 30 and 7 percent of doctors between the ages of 30 and 35, practicing in Darrenville, made at least one avoidable error during a medical procedure. On the other hand, only 2 percent of doctors 60 and older made such an error. These findings make it clear that the advanced experience and learned propensity for caution possessed by doctors in the 60 and older group make them far more reliable than younger doctors are.
Which of the following is an assumption on which the argument depends?
(A) The difference between the error rate of doctors under 30 and of those between 30 and 35 can be attributed to the higher level of medical experience possessed by the older doctors.
(B) Doctors 60 years and above do not make up a meaningfully larger fraction of physicians in Darrenville than doctors between the ages of 30 and 35 do.
(C) Doctors 60 years and above are less likely than are doctors 35 and younger to perform medical procedures under circumstances that significantly heighten the risk of errors.
(D) Doctors 60 years and above, on average, do not, treat a considerably lower number of patients per year than doctors 35 and younger do.
(E) For no age bracket is the error rate lower than it is for doctors 60 and older.
Which of the following is an assumption on which the argument depends?
(A) The difference between the error rate of doctors under 30 and of those between 30 and 35 can be attributed to the higher level of medical experience possessed by the older doctors.
(B) Doctors 60 years and above do not make up a meaningfully larger fraction of physicians in Darrenville than doctors between the ages of 30 and 35 do.
(C) Doctors 60 years and above are less likely than are doctors 35 and younger to perform medical procedures under circumstances that significantly heighten the risk of errors.
(D) Doctors 60 years and above, on average, do not, treat a considerably lower number of patients per year than doctors 35 and younger do.
(E) For no age bracket is the error rate lower than it is for doctors 60 and older.
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15 Dec 2025, 10:00
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Bunuel
Experts' Global Official Solution:
Mind-map: Higher percentage of two groups of younger than 35 doctors made at least one avoidable error à lower percentage of doctors over 60 made such error à more experience and learned caution of the doctors over 60 make them more reliable than younger doctors (conclusion)
Missing-link: Between all the information presented and the conclusion that more experience and learned caution of the doctors over 60 make them more reliable than younger doctors
Expectation from the correct answer choice: To strengthen the conclusion that more experience and learned caution of the doctors over 60 make them more reliable than younger doctors, through a valid assumption
A. Trap. This answer choice, suggesting that the difference in the error rate of doctors between 30 and 35 and of doctors younger than 30 is attributed to more experience, emphasizes the importance of experience but does not rule out the possibility that the lower error rate by doctors over 60 may be because of a factor unrelated to higher experience; so, this answer choice, at best, only marginally strengthens the conclusion. However, despite being a mild "strengthening statement", this answer choice doesn't qualify as a valid "assumption" because it doesn't have to be true for the conclusion to hold; it is possible that the conclusion holds even if the difference in the error rate of doctors between 30 and 35 and of doctors younger than 30 is attributed to any reason other than more experience; please remember, a valid assumption “must be necessarily true” for the argument to hold. Because this answer choice does not strengthen the conclusion through a valid assumption, this answer choice is incorrect.
B. Trap. The argument compares the number of doctors that make an error with the total number of doctors in the same age group; so, whether a particular age group of doctors is larger than other age groups has no bearing on the argument; hence, this answer choice, comparing the size of the age group of doctors over 60 and the size of the age group of doctors between 30 and 35, does not strengthen the argument. Besides, this condition is not necessary for the argument to hold and thus, is not a valid assumption. Because this answer choice does not strengthen the conclusion through a valid assumption, this answer choice is incorrect.
C. Trap. This answer choice, suggesting that doctors over 60 are less likely to perform error-prone procedures, indicates that the doctors over 60 have a lower error rate possibly because of lower risk of errors, thus introducing an alternate cause and weakening, rather than strengthening, the conclusion. Because this answer choice does not strengthen the conclusion through a valid assumption, this answer choice is incorrect.
D. Correct. By suggesting that the number of patients treated per year by doctors over 60 is not significantly lower than that by doctors below 35, this answer choice eliminates the possibility that the lower error rate by doctors over 60 is likely because of the fewer number of treatments performed; hence, this answer choice eliminates an alternate cause and strengthens the conclusion. Additionally, this statement does have to be true for the conclusion to hold; negating this statement would mean that “the number of patients treated per year by doctors over 60 is significantly lower than that by doctors below 35”, thus casting doubt on whether fewer treatments performed is a likely cause for the lower error rate and negating the conclusion. Because this answer choice strengthens the conclusion through a valid assumption, this answer choice is correct.
E. Trap. This answer choice, suggesting that no age group of doctors has a lower error rate than that of doctors 60 and older, indicates that doctors over 60 are likely most reliable; highest reliability in the oldest age group of doctors marginally strengthens the conclusion that more experience of the doctors over 60 makes them more reliable than younger doctors. However, despite being a mild "strengthening statement", this answer choice doesn't qualify as a valid "assumption" because it doesn't have to be true for the conclusion to hold; it is possible that the conclusion holds even if there is an age group of doctors that has an error rate equal to or slightly more than that of doctors 60 and older; please remember, a valid assumption “must be necessarily true” for the argument to hold. Further, please note, a hint here is in the term “no age bracket”, which is too strong to be a valid assumption; one needs to be cautious of such answer choices as they are generally incorrect on the GMAT. Because this answer choice does not strengthen the conclusion through a valid assumption, this answer choice is incorrect.
D is the best choice.
General Discussion
15 Dec 2025, 09:45
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Let's eliminate the options one by one:
A. Misstates evidence; focuses on under-30 vs 30-35 difference, irrelevant to older vs. younger comparison.
B. Addresses group sizes, but percentages already normalize this.
C. Introduces external risk factors, not required.
E. Claims lower rate overall so eliminate.
Correct answer: D
A. Misstates evidence; focuses on under-30 vs 30-35 difference, irrelevant to older vs. younger comparison.
B. Addresses group sizes, but percentages already normalize this.
C. Introduces external risk factors, not required.
E. Claims lower rate overall so eliminate.
Correct answer: D
