Last visit was: 21 Apr 2026, 00:41 It is currently 21 Apr 2026, 00:41
Home
Messages
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
   1   2   3   4   
655-705 (Hard)|   Assumption|         
User avatar
KavyaD17
User avatar
Joined: 19 Nov 2024
Last visit: 20 Apr 2026
Posts: 31
Own Kudos:
13
 [1]
Given Kudos: 60
Location: India
Concentration: Finance
GMAT Focus 1: 615 Q82 V83 DI76
Products:
GMAT Club Tests Forum Quiz
GMAT Focus 1: 615 Q82 V83 DI76
Posts: 31
Kudos: 13
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:06
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
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.
Show more

The argument assumes that it is the lower error rate that truly reflects greater reliability, not some other factor that artificially lowers the probability of committing an error.

If older doctors perform fewer procedures, they would naturally have a lower chance of making at least one error, even if they were no more reliable. So the argument must assume that older people are not simply seeing far fewer patients. Therefore, answer is choice D.
User avatar
veroaperiam
User avatar
Joined: 29 Oct 2025
Last visit: 08 Apr 2026
Posts: 8
Own Kudos:
7
Given Kudos: 36
Location: India
Schools: INSEAD Jan '27 HEC ISB '27
GPA: 3.76
Schools: INSEAD Jan '27 HEC ISB '27
Posts: 8
Kudos: 7
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:08
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Answer (E). If we negate this assumption, then the whole conclusion falls apart.

Bunuel
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.
Show more
User avatar
Saks116
User avatar
Joined: 05 Apr 2022
Last visit: 20 Apr 2026
Posts: 41
Own Kudos:
22
Given Kudos: 32
Location: India
Products:
Forum Quiz
Posts: 41
Kudos: 22
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:16
Kudos
Add Kudos
Bookmarks
Bookmark this Post
D
if we take an account of fraction, the Dr. ageing above 60 handles the no. patients and Dr. <35 age handling the patient
User avatar
vasu1104
User avatar
Joined: 10 Feb 2023
Last visit: 20 Apr 2026
Posts: 388
Own Kudos:
233
Given Kudos: 664
Location: Canada
Products:
Forum Quiz
Posts: 388
Kudos: 233
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:30
Kudos
Add Kudos
Bookmarks
Bookmark this Post
conclusion- advanced ecpereince and learning propensity make doctors older than 60 years more reliable than younger ones.
A= conclusion says same thing that experience is key for higher reliance on doctors older than 60.e reject it.\
B= what about doctors younger than 30. reject it.
C= if they are less likely to perform under situation where they dont make errors then its not experience or knowledge but less extreme condition for lower error rate. perfect.
D= negation makes it weakening conclusion. it says they treat less patients. so gonna make less erros. reject it.
E= no impact at all.
Bunuel
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.
Show more
User avatar
aka007
User avatar
Joined: 15 Nov 2019
Last visit: 19 Mar 2026
Posts: 42
Own Kudos:
37
Given Kudos: 84
Posts: 42
Kudos: 37
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:33
Kudos
Add Kudos
Bookmarks
Bookmark this Post
The argument is based on the premise that higher the experience of doctors the lesser is the chance of human error. However, the doctors considers only three age groups i.e. Below 30, 30 to 35 and above 60. However, if there exists an age group lesser than 60 that is making lesser than 2% errors then this argument is flawed. Hence, this argument relies on the fact that there is no such age group of doctors below 60 making lesser errors.

Hence E is the answer.

Bunuel
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.
Show more
User avatar
gaganabbot
User avatar
Joined: 12 Apr 2022
Last visit: 10 Mar 2026
Posts: 3
Given Kudos: 1
Posts: 3
Kudos: 0
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:36
Kudos
Add Kudos
Bookmarks
Bookmark this Post
but what if doctors over 60 do fewer procedures overall wouldn’t that explain lower error rate

Bunuel
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.
Show more
User avatar
suntincidunt
User avatar
Joined: 08 Dec 2025
Last visit: 16 Dec 2025
Posts: 8
Own Kudos:
3
Posts: 8
Kudos: 3
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:41
Kudos
Add Kudos
Bookmarks
Bookmark this Post
D. Percentages makes more sense when the sample sie is big enough and not biased.

Bunuel
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.
Show more
User avatar
harishg
User avatar
Joined: 18 Dec 2018
Last visit: 09 Apr 2026
Posts: 176
Own Kudos:
174
 [1]
Given Kudos: 31
GMAT Focus 1: 695 Q88 V84 DI81
Products:
My Reviews Forum Quiz
GMAT Focus 1: 695 Q88 V84 DI81
Posts: 176
Kudos: 174
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 11:52
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
A - we are not worried about the difference in error rate between below 30 and 30-35 age doctors, but those above 60. Therefore, the option is not within scope.

B - The option dies not talk about doctors 30 and below. The number of doctors doing errors in that segment might still be higher and the argument valid.

C - The statement given is a weakener to the argument and therefore cannot be an assumption.

D - If the negation of this option is true, it gives an alternate reason to the effect, thereby weakening the argument. This is our answer.

E - we do not have to assume that error rate is the lowest in 60 year and above segment.

Therefore, Option D.
User avatar
obedear
User avatar
Joined: 05 Sep 2024
Last visit: 20 Apr 2026
Posts: 61
Own Kudos:
39
 [1]
Given Kudos: 11
Products:
GMAT Club Tests Forum Quiz
Posts: 61
Kudos: 39
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 12:10
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I selected D.

My strategy for assumption questions is to negate the answer choices and see if the argument falls apart.

A - This would be a good choice if it was comparing the doctors who are 60 and older to the younger groups, however the argument is that the 60 and older age group are committing less errors due to their age, it does not matter if the difference in error rates between the 30 and 30-35 group are not attributable to medical experience, as they are still significantly higher than the 10%.

B - If they do make up a larger amount, then it would support the argument even more because a higher percentage of the group would be committing less errors.

C - If the 60+ age group are more likely to accept/perform operations that are more risky, then it would strengthen the argument because their error rate is so low despite accepting operations that have an inherently increased risk.

D - If they treat a lower number of patients then other groups, then an alternative explanation is that the low amount of errors is due to the low number of cases of procedures, and that the error rate might align if the number of procedures was the same.

E - Just because there is a younger age bracket with a lower error rate does not mean the older doctors are not committing less errors due to their experience.
User avatar
AviNFC
User avatar
Joined: 31 May 2023
Last visit: 10 Apr 2026
Posts: 306
Own Kudos:
366
 [1]
Given Kudos: 5
Posts: 306
Kudos: 366
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 12:26
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
(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.Wrong.This supports, need not be assumed

(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.Wrong. While this may b true, the problems reamins that few aged doctors availble are better

(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.Wrong..Opposite. If they are working in risky environment also,then supports that r they skilled

(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.Correct. If aged doctors are handling fewer cases, then error data cannot be validated

(E) For no age bracket is the error rate lower than it is for doctors 60 and older.Wrong..Irrelevant as the fact still holds.

Ans D
User avatar
SSWTtoKellogg
User avatar
Joined: 06 Mar 2024
Last visit: 20 Apr 2026
Posts: 90
Own Kudos:
58
 [1]
Given Kudos: 20
Location: India
Schools: INSEAD Jan '27
GMAT Focus 1: 595 Q83 V78 DI77
GMAT Focus 2: 645 Q87 V79 DI79
GPA: 8.8
Schools: INSEAD Jan '27
GMAT Focus 2: 645 Q87 V79 DI79
Posts: 90
Kudos: 58
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 12:28
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
D - Removal of probable weakness that there is no less number of patient treatment by 60+ doctors.
User avatar
canopyinthecity
User avatar
Joined: 12 Jul 2025
Last visit: 17 Apr 2026
Posts: 91
Own Kudos:
61
Given Kudos: 19
Posts: 91
Kudos: 61
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 12:38
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Main Point: 60 and older group are more reliable than younger doctors are.
Basis: 10% of <30, 7% of 30-35 and 2% of >60 made at least one avoidable error during a medical procedure
Logic: Since 60 and older group made the least error out of the 3 groups, they must be more reliable.
Gaps: (1) What is 35-60 group have less error than all three groups provided?
(2) The number of 60 and older groups might be quite low
(3) The risky operations do not come to older group

Options:
(A) Irrelevant to the argument
(B), (C) and (D) - This are the gaps in the logic, but this is not the assumption in the argument

(E) is an assumption, as only based on this, the author can conclude that 60 and older are more reliable than the rest!
User avatar
jkkamau
User avatar
Joined: 25 May 2020
Last visit: 20 Apr 2026
Posts: 226
Own Kudos:
190
 [1]
Given Kudos: 142
Location: Kenya
Schools: Haas '25
GMAT 1: 730 Q50 V46
GPA: 3.5
Products:
Forum Quiz
Schools: Haas '25
GMAT 1: 730 Q50 V46
Posts: 226
Kudos: 190
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 13:17
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
A: Irrelevant
B. Irrelevant
c. Doesn't change the outcome
d. Correct. If this is the case then the explanation breaks down
e. Does not explain the discrepancy
Bunuel
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.
Show more
User avatar
Rishi705
User avatar
Joined: 25 Apr 2024
Last visit: 02 Feb 2026
Posts: 53
Own Kudos:
41
Given Kudos: 21
Posts: 53
Kudos: 41
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 13:20
Kudos
Add Kudos
Bookmarks
Bookmark this Post
OK, let's break down the argument

The first states of fact where dimensions to group of doctors and their respective rates of errors
The second introduces a third group of doctors and showcases it's considerably lower rate of error.
Based on it, it draws a conclusion Advanced experience and for caution make doctors more reliable when they go 60 or older.

What assumptions do they need?
The situation in which the two age groups of doctors are operating are not very different in terms of technological advancements or patient health and so on.

1. The difference of errors made between the first groups not necessarily be attributed to age, maybe only after a few decades of additional experience, does the higher caliber start to show.

2. This says that the number of younger Doctors is greater than the number of older doctors. but we don't have an absolute number of errors we have a percent of errors so there are 100 doctors operating two of them made a mistake, if 1000 or operating 20 made mistake. It does not discount their low rate of error.

3. This statement says that they are cautious, I hold onto the option.

4. Option for trip me up for a bit, but the same logic for option two can be applied here as well, as long as it doesn't mention a difference in the condition of the patient that they are treating. I don't know what I can do with this statement..

5. maybe 75 make one percent errors, maybe all doctors over 120 years of age don't make any errors because they're all dead, but certainly doesn't impact the statement about my 60 year old doctors.

I was a little confused the correct answer did not match with my pre-thinking, but that happens often. it does restate a crucial part of the evidence, statement says that they are not cautious, and my evidence says that it is their caution that makes them safe, so I go with option C
Bunuel
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.
Show more
User avatar
Natansha
User avatar
Joined: 13 Jun 2019
Last visit: 11 Mar 2026
Posts: 195
Own Kudos:
65
Given Kudos: 84
Posts: 195
Kudos: 65
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 13:25
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Conclusion is since the percent error of 60+ doctors is less than the younger ones, they are more reliable.

A) not relevant as the comparison is not between the two categories of young doctors.
E) not relevant as it is the conclusion stated again that percent is less for 60+ than for others
C) If we negate C, then 60+ doctors are more likely to work in circumstances that heights the risk of error yet their errors are less, doesnt break the conclusion, eliminated.
B) Thought it made sense but the comparison is between young doctors and 60+, not just with the doctors in the age bracket of 30-35

Which leaves us with D, which makes the most sense, negating it, 60+ doctors treat lower no of patients than younger doctors, which break the conclusion that it is age which lowers the error rate, and says that if they treat less patients, they will have lower error rate. Hence ans (D)
User avatar
Nitish03
User avatar
Joined: 02 Feb 2025
Last visit: 20 Apr 2026
Posts: 46
Own Kudos:
20
Given Kudos: 28
Location: India
Posts: 46
Kudos: 20
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 14:33
Kudos
Add Kudos
Bookmarks
Bookmark this Post
- Answer D
As the findings focuses on experience and learned propensity for caution possessed by doctors , the arguments depends on assumption that 60 plus doctors do not treat fewer patients than younger ones.
User avatar
Harika2024
User avatar
Joined: 27 Jul 2024
Last visit: 16 Mar 2026
Posts: 99
Own Kudos:
84
Given Kudos: 31
Location: India
Posts: 99
Kudos: 84
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 15:36
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Lets breakdown the question

1. We have data : Younger doctor under 30 = 10% error rate, Mid age doctor ( 30 to 35) = 7% error rate and older doctors = 2% error rate.

2. The lower error rate of older doctors groups is due to their advanced experience and learned caution, making them far more reliable than younger doctors.

here error rate statistics to conclude that older doctors personal experience or caution make them more reliable. For comparison to accurately reflect the doctors reliability , circumstances under which they practice must be comparable. if older doctors are generally practicing under less risky or less challenging conditions, difference in error rate might be due to procedures they perform, not their skill or caution. The argument must assume that difference in error rate is due to doctors experience or caution, not external circumstances.

Now lets check the options:


Option A : This just explain about difference between younger groups . The core argument is between younger group and older group. This argument could stand even if 30 to 35 group lower rate was due to something else.

Option B : The size of the group doesnt matter for the percentage based conclusion.

Option C : This is the necessary assumption, If older doctors consistently take on only less risky surgeries, their 2 % error rate might be expected and not evidence of greater reliability when compared to difficulty faced by younger doctors. if this statement were false, the entire conclusion that their low rate proves their superior reliability could crumble.

Option D : The error rate is calculated based on number of doctors who made at least one error. this rate is independent of total number of patients treated as long as doctors treated enough patients to have a chance to make an error.

Option E : This only compares older group to younger groups. It is irrelevant to the comparison the scientist actually makes

Therefore the correct option is C
User avatar
SafSin28
User avatar
Joined: 16 Aug 2022
Last visit: 20 Apr 2026
Posts: 84
Own Kudos:
67
 [1]
Given Kudos: 60
Posts: 84
Kudos: 67
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 19:25
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
QS: Assumption

Argument: 10% of doctors younger than 30, 7 % of doctors aged between 30 and 35 make avoidable mistakes. BUT 2 % of doctors aged 60+ make such mistakes. CONCLUSION doctors aged 60+ are more reliable than doctors aged 35-.

A) This is about the difference between 30- and 30-35 aged doctors. A fact checker. It does not do anything with the conclusion. OUT
B) This is about the comparative fraction of the doctors. Off context of the argument. It does not lead to the conclusion. OUT.
C) This is a possible a weakener. When this is true, it weakens the conclusion. OUT
D) This must be true for the conclusion to be true. If negated it weakens the argument. Keep it.
E) No age group performs better than 60+ doctors. This does not explain how conlusion is true. So OUT

D is a winner here
User avatar
bhanu29
User avatar
Joined: 02 Oct 2024
Last visit: 20 Apr 2026
Posts: 358
Own Kudos:
267
 [1]
Given Kudos: 262
Location: India
Schools: Anderson '27 Booth '27 Foster '27 Haas '27 Kellogg '27 Kellogg Mashall '27 McCombs '27 Ross '27 Scheller '27 Tepper '27 Yale '27 Sloan (MIT) Stanford '27
GMAT Focus 1: 675 Q87 V85 DI79
GMAT Focus 2: 715 Q87 V84 DI86
GPA: 9.11
WE:Engineering (Technology)
Products:
My Reviews GMAT Club Tests Forum Quiz
Schools: Anderson '27 Booth '27 Foster '27 Haas '27 Kellogg '27 Kellogg Mashall '27 McCombs '27 Ross '27 Scheller '27 Tepper '27 Yale '27 Sloan (MIT) Stanford '27
GMAT Focus 2: 715 Q87 V84 DI86
Posts: 358
Kudos: 267
 [1]
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 19:43
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
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.
Show more
The argument concludes that doctors 60+ are "far more reliable" because of their experience and caution, based solely on comparing error rate percentages. For this comparison to be valid, the argument must assume those percentages reflect a fair comparison.

(A) The difference between error rates of under-30 vs. 30-35 doctors can be attributed to experience.
This explains the gap between two younger groups, but the argument is comparing 60+ doctors to younger doctors overall - this isn't necessary for that main conclusion.

(B) Doctors 60+ don't make up a meaningfully larger fraction of physicians than 30-35 doctors do.
Error rates (percentages) already account for group size, so the proportion of doctors in each bracket doesn't matter to the reliability comparison.

(C) Doctors 60+ are less likely to perform procedures under high-risk circumstances.
Actually, if this were true, it would weaken the argument by providing an alternative explanation for the lower error rate. The argument doesn't depend on this. If the it was not less likely than it would have been an assumption as it eliminates the alternative explanation.

(D) Doctors 60+, on average, don't treat considerably fewer patients per year than younger doctors.

This is the necessary assumption. Here's why it matters: If older doctors saw 10 patients per year while younger doctors saw 1,000, the 2% error rate comparison would be meaningless. You can't claim someone is "far more reliable" when they're operating at a completely different volume of work. The lower error rate might just reflect limited exposure, not superior skill or caution. To verify this is necessary, use the negation test: If doctors 60+ do treat considerably fewer patients, the argument falls apart because the error rate no longer proves greater reliability. That's exactly what makes this a necessary assumption - without it, the conclusion can't stand.

(E) For no age bracket is the error rate lower than 60+.
This just restates information already given in the passage without adding anything necessary to support the conclusion.

Correct Answer D
User avatar
flippedeclipse
User avatar
Joined: 26 Apr 2025
Last visit: 20 Apr 2026
Posts: 105
Own Kudos:
73
Given Kudos: 37
GMAT Focus 1: 655 Q80 V87 DI80
Products:
My Reviews
GMAT Focus 1: 655 Q80 V87 DI80
Posts: 105
Kudos: 73
12 Days of Christmas GMAT Competition 2025 - Day 1: Last year, 10 15 Dec 2025, 19:44
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
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.
Show more

Let's go through the argument first.

Sentence 1: 10% of < 30-year-old doctors and 7% of 30-35-year-old doctors made an avoidable mistake.
Sentence 2: 2% of doctors over 60 made a mistake.
Sentence 3: Conclusion - older doctors are more reliable than younger doctors.

We're looking for an answer choice that this argument depends on. In other words, we're looking for something that, without, this argument falls apart.

Let's get started.

Option A: 30 or less is being compared to 30-35 here, which is not what the conclusion is discussing. Irrelevant, eliminate.
Option B: Let's test with some numbers. Say there's 1,000 60+ doctors, 2% of which means they made 20 mistakes collectively. Now lets say there's 100 30-35 & 100 <30 doctors, who made 17 mistakes collectively. This would mean older doctors actually make more mistakes in total than younger doctors, which would break the argument. Let's hold onto this one.
Option C: If older doctors perform less risky medical procedures than younger doctors, that would indeed cause them to make less mistakes. However, this doesn't form the assumption of this argument - while it would explain the discrepancy, but it does not identify the assumption.
Option D: Let's say <35 doctors treat 1000 patients, 60+ doctors treat 100 patients. Assuming 50/50 for the two younger age groups, they will make 85 mistakes, and the older doctors will make two mistakes. This corresponds well with the argument, and if this was untrue, it wouldn't have much of an effect on the argument, because the numbers go along with what's already stated in the argument. In essence, if this option breaks, it does not break the argument.
Option E: Older doctors being the lowest error rate overall is a nice fact, but even without it, the argument remains intact.

Option B is the only option that, without, the argument can't survive and is the answer.
   1   2   3   4   
Moderators:
GMATNinja
GMAT Club Verbal Expert
7391 posts
AbhishekP220108
494 posts
bhanu29
358 posts