Last visit was: 17 Jul 2025, 21:13 It is currently 17 Jul 2025, 21:13
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.
Close
Request Expert Reply
Confirm Cancel
User avatar
carcass
User avatar
Board of Directors
Joined: 01 Sep 2010
Last visit: 17 Jul 2025
Posts: 4,726
Own Kudos:
36,192
 [34]
Given Kudos: 4,813
Posts: 4,726
Kudos: 36,192
 [34]
1
Kudos
Add Kudos
33
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Ashishmathew01081987
Joined: 20 Jan 2013
Last visit: 07 Jun 2020
Posts: 93
Own Kudos:
304
 [6]
Given Kudos: 71
Status:I am not a product of my circumstances. I am a product of my decisions
Location: India
Concentration: Operations, General Management
GPA: 3.92
WE:Operations (Energy)
Posts: 93
Kudos: 304
 [6]
3
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
User avatar
shameekv
Joined: 29 Aug 2013
Last visit: 11 Aug 2020
Posts: 50
Own Kudos:
178
 [5]
Given Kudos: 26
Location: United States
Concentration: Finance, International Business
GMAT 1: 590 Q41 V29
GMAT 2: 540 Q44 V20
GPA: 3.5
WE:Programming (Computer Software)
GMAT 2: 540 Q44 V20
Posts: 50
Kudos: 178
 [5]
2
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
General Discussion
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 17 Jul 2025
Posts: 102,605
Own Kudos:
742,308
 [2]
Given Kudos: 98,220
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 102,605
Kudos: 742,308
 [2]
1
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
shameekv
carcass
A researcher investigating mosquito populations recorded a list of estimates of mosquito populations at each of \(n\) different marshland locations in a certain country. The distribution of these estimates was symmetric about the average (arithmetic mean), and 70% of these population estimates were within one standard deviation of the mean. Of these estimates, 75 were more than one standard deviation below the mean. Approximately how many of the estimates were within one standard deviation of the mean?

A) 175
B) 350
C) 375
D) 425
E) 500


If 70% of population is within 1 standard deviation mean then 30% are more than 1 standard deviation below the mean.

Taking symmetric about the mean,
75 are more than 1 sd below the mean therefore these 75 constitute 15% (Taking 15% below the mean and 15% above the mean)

Therefore total population is 500.

Therefore 70% of 500 is 350. who are within 1 standard deviation from the mean.

Hence B

Similar questions to practice:
arithmetic-mean-and-standard-deviation-of-a-certain-normal-104117.html
70-75-80-85-90-105-105-130-130-130-the-list-shown-consist-of-100361.html
for-a-certain-exam-a-score-of-58-was-2-standard-deviations-b-128661.html
a-certain-characteristic-in-a-large-population-has-a-143982.html
a-vending-machine-is-designed-to-dispense-8-ounces-of-coffee-93351.html
the-residents-of-town-x-participated-in-a-survey-83362.html
the-standard-deviation-of-a-normal-distribution-of-data-is-99221.html
the-mean-and-the-standard-deviation-of-the-8-numbers-shown-98248.html
the-lifetime-of-all-the-batteries-produced-by-a-certain-comp-101472.html

Hope it helps.
avatar
annasejahat
Joined: 17 Dec 2012
Last visit: 01 Jul 2021
Posts: 25
Own Kudos:
Given Kudos: 38
Concentration: General Management, Entrepreneurship
GMAT 1: 660 Q44 V37
GMAT 1: 660 Q44 V37
Posts: 25
Kudos: 5
Kudos
Add Kudos
Bookmarks
Bookmark this Post
So guys, i did an error that 30% rather than 15% of population is at the left hand side of the distribution. So I guess in a normal distribution it must symmetry at both sides (duh!)
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 37,444
Own Kudos:
Posts: 37,444
Kudos: 1,013
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderators:
Math Expert
102605 posts
PS Forum Moderator
698 posts