GRE Prep 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.
If a certain sample of data has a mean of 20.0 and a standar
[#permalink]
14 Sep 2020, 10:23
14 Sep 2020, 10:23
Expert Reply
2
Bookmarks
00:00
Question Stats:
67% (00:47) correct
32% (00:59) wrong based on 31 sessions
Hide Show timer Statistics
If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?
A. 12.0
B. 13.5
C. 17.0
D. 23.5
E. 26.5
Source: GMAT
A. 12.0
B. 13.5
C. 17.0
D. 23.5
E. 26.5
Source: GMAT
Re: If a certain sample of data has a mean of 20.0 and a standar
[#permalink]
14 Sep 2020, 10:23
14 Sep 2020, 10:23
Expert Reply
1
Bookmarks
Post A Detailed Correct Solution For The Above Questions And Get A Kudos.
Question From Our New Project: GRE Quant Challenge Questions Daily - NEW EDITION!
For more theory and practice see our GRE - Math Book
Question From Our New Project: GRE Quant Challenge Questions Daily - NEW EDITION!
For more theory and practice see our GRE - Math Book
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If a certain sample of data has a mean of 20.0 and a standar
[#permalink]
14 Sep 2020, 10:37
14 Sep 2020, 10:37
1
Carcass wrote:
If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?
A. 12.0
B. 13.5
C. 17.0
D. 23.5
E. 26.5
Source: GMAT
A. 12.0
B. 13.5
C. 17.0
D. 23.5
E. 26.5
Source: GMAT
-------ASIDE----------
A little extra background on standard deviations above and below the mean
If, for example, a set has a standard deviation of 4, then:
1 standard deviation = 4
2 standard deviations = 8
3 standard deviations = 12
1.5 standard deviations = 6
0.25 standard deviations = 1
etc
So, if the mean of a set is 9, and the standard deviation is 4, then:
2 standard deviations ABOVE the mean = 17 [since 9 + 2(4) = 17]
1.5 standard deviations BELOW the mean = 3 [since 9 - 1.5(4) = 3]
3 standard deviations ABOVE the mean = 21 [since 9 + 3(4) = 21]
etc.
-----------------------------
So, 2.5 standard deviations = (2.5)(3) = 7.5
20 - 7.5 = 12.5
So, 12.5 is 2.5 standard deviations BELOW the mean
20 + 7.5 = 27.5
So, 27.5 is 2.5 standard deviations ABOVE the mean
Answer choice A (12) is more than 2.5 standard deviations from the mean
Answer: A
