Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Jun 0612:30 AM EDT
-01:30 AM EDT
Struggling to find the right strategies to score a 99 %ile on GMAT Focus? Riya (GMAT 715) boosted her score by 100-points in just 15 days! Discover how the right mentorship, tailored strategies, and an unwavering mindset can transform your GMAT prep.
Jun 0701:30 AM EDT
-02:30 AM EDT
Learn how Kamakshi achieved a GMAT 675 with an impressive 96th %ile in Data Insights. Discover the unique methods and exam strategies that helped her excel in DI along with other sections for a balanced and high score.
Jun 0803:00 PM PDT
-04:00 PM PDT
15 Full-length GMAT FE mocks with insightful analytics, weakness diagnosis, and video explanations!
Jun 0808:00 PM EDT
-10:00 PM EDT
A powerful GMAT course taught live online + 6 months of access to TTP OnDemand GMAT Masterclass included! Class begins June 8, 2026
Jun 1006:00 AM PDT
-06:15 PM PDT
Register for the GMAT Club Virtual MBA Spotlight Fair – the world’s premier event for serious MBA candidates. This is your chance to hear directly from Admissions Directors at nearly every Top 30 MBA program..
Jun 1111:00 AM EDT
-01:00 PM EDT
TTP GMAT OnDemand gives serious students 400+ hours of expert video instruction, the full TTP course, AI support, weekly office hours, and a 715+ score guarantee—all built for elite GMAT score improvement.
24 Dec 2025, 09:00
Kudos
Bookmarks
Most decrease: 56
Most increase: 38
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
56% (02:19) correct
44%
(02:42)
wrong
based on 231
sessions
History
Date
Time
Result
Not Attempted Yet
12 Days of Christmas Competition
This question is part of our holiday event
Win $40,000 in prizes: courses, tests, and more
A quality inspector recorded the fill volumes, in milliliters, of six bottles from a production run, with the following results:
{24, 38, 53, 23, 56, 34}
The inspector believes exactly one of the six measurements is erroneous and will discard that measurement. To evaluate the impact of the discard, he will calculate the standard deviation of the original six measurements and the standard deviation of the remaining five measurements.
Select for Most decrease the measurement which, if discarded, would produce the greatest decrease in standard deviation, and select for Most increase the measurement which, if discarded, would produce the greatest increase in standard deviation. Make only two selections, one in each column.
I31-34
| Most decrease | Most increase | |
| 23 | ||
| 24 | ||
| 34 | ||
| 38 | ||
| 53 | ||
| 56 |
ShowHide Answer
Official Answer
Most decrease: 56
Most increase: 38
24 Dec 2025, 10:00
Kudos
Bookmarks
A quality inspector recorded the fill volumes, in milliliters, of six bottles from a production run, with the following results:
{24, 38, 53, 23, 56, 34}
The inspector believes exactly one of the six measurements is erroneous and will discard that measurement. To evaluate the impact of the discard, he will calculate the standard deviation of the original six measurements and the standard deviation of the remaining five measurements.
Select for Most decrease the measurement which, if discarded, would produce the greatest decrease in standard deviation, and select for Most increase the measurement which, if discarded, would produce the greatest increase in standard deviation. Make only two selections, one in each column.
First find the mean of the original six measurements.
Mean = (23 + 24 + 34 + 38 + 53 + 56)/6 = 38.
Standard deviation depends on how far the numbers are from the mean (and larger distances matter much more).
Most decrease:
Removing the single value with the largest absolute distance from the mean reduces the standard deviation the most. 56 is farthest from the mean 38 (it is 18 away). Since it has the largest distance from the mean, discarding 56 reduces the spread the most. So Most decrease is 56.
Most increase:
38 is exactly the mean, so it contributes the least deviation among the six numbers: zero. Hence, discarding 38 removes none of the “spread” but leaves only five numbers with the same mean of 38, so the average spread among the remaining values becomes larger. This produces the greatest increase in standard deviation. Thus, removing an item whose value is equal to the mean value makes the set more widespread, increasing the standard deviation. So Most increase is 38.
GMAT-Club-Forum-ywx7rw4v.png [ 14.32 KiB | Viewed 1519 times ]
{24, 38, 53, 23, 56, 34}
The inspector believes exactly one of the six measurements is erroneous and will discard that measurement. To evaluate the impact of the discard, he will calculate the standard deviation of the original six measurements and the standard deviation of the remaining five measurements.
Select for Most decrease the measurement which, if discarded, would produce the greatest decrease in standard deviation, and select for Most increase the measurement which, if discarded, would produce the greatest increase in standard deviation. Make only two selections, one in each column.
GMAT Club Official Explanation:
First find the mean of the original six measurements.
Mean = (23 + 24 + 34 + 38 + 53 + 56)/6 = 38.
Standard deviation depends on how far the numbers are from the mean (and larger distances matter much more).
Most decrease:
Removing the single value with the largest absolute distance from the mean reduces the standard deviation the most. 56 is farthest from the mean 38 (it is 18 away). Since it has the largest distance from the mean, discarding 56 reduces the spread the most. So Most decrease is 56.
Most increase:
38 is exactly the mean, so it contributes the least deviation among the six numbers: zero. Hence, discarding 38 removes none of the “spread” but leaves only five numbers with the same mean of 38, so the average spread among the remaining values becomes larger. This produces the greatest increase in standard deviation. Thus, removing an item whose value is equal to the mean value makes the set more widespread, increasing the standard deviation. So Most increase is 38.
Attachment:
GMAT-Club-Forum-ywx7rw4v.png [ 14.32 KiB | Viewed 1519 times ]
General Discussion
24 Dec 2025, 09:54
Kudos
Bookmarks
Mean = (24+38+53+23+56+34)/6 = 38
Max decrease in SD happens when a value farthest away from mean is removed, which is 56
Max increase in SD happens when a value closest to mean is removed, which is 38, the mean itself
| Values | 23 | 24 | 34 | 38 | 53 | 56 | |
| Difference from Mean | -15 | -14 | -4 | 0 | 15 | 28 | |
Max decrease in SD happens when a value farthest away from mean is removed, which is 56
Max increase in SD happens when a value closest to mean is removed, which is 38, the mean itself
Bunuel
