BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

To find the same standard deviation

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 641
Joined: Tue Feb 14, 2012 3:52 pm
Thanked: 11 times
Followed by:8 members

To find the same standard deviation

by gmattesttaker2 » Sat Jan 11, 2014 6:39 pm
Hello,

Can you please assist with this:

Which of the following sets has the same standard deviation as set {m, n, p, q, r}?

A) {m/2,n/2,p/2,q/2,r/2}
B) { m^2, n^2, p^2, q^2, r^2 }
C) {m + 2, n + 2, p + 2, q + 2, r + 2}
D) {2m,2n,2p,2q,2r}
E) {|m|,|n|,|p|,|q|,|r|}

OA: C


I was wondering when will E be wrong since absolute value will always be positive.

Thanks a lot.

Best Regards,
Sri
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 490
Joined: Thu Jul 04, 2013 7:30 am
Location: Chennai, India
Thanked: 83 times
Followed by:5 members

by Uva@90 » Sat Jan 11, 2014 7:17 pm
gmattesttaker2 wrote:Hello,

Can you please assist with this:

Which of the following sets has the same standard deviation as set {m, n, p, q, r}?

A) {m/2,n/2,p/2,q/2,r/2}
B) { m^2, n^2, p^2, q^2, r^2 }
C) {m + 2, n + 2, p + 2, q + 2, r + 2}
D) {2m,2n,2p,2q,2r}
E) {|m|,|n|,|p|,|q|,|r|}

OA: C


I was wondering when will E be wrong since absolute value will always be positive.

Thanks a lot.

Best Regards,
Sri
Hi Sri,
The Concept behind this question is,
If we add or subtract a constant to each term in a set Mean will increase or decrease by the same constant SD will not change.

Considering the above statement Answer will be C

Coming to you question
Why Not E?
E option will always be Positive, but set {m, n, p, q, r} may have negative values, as
Let set {2,-2,-1,1} wil not have same SD as {2,2,1,1}

Hope I made it clear.

Earlier even I had same confusion. Later Brent and Mitch had explained me clearly.
Here is the link for the same,
https://www.beatthegmat.com/standard-dev ... tml#701110

Regards,
Uva
Known is a drop Unknown is an Ocean
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sat Jan 11, 2014 9:39 pm
gmattesttaker2 wrote:Hello,

Can you please assist with this:

Which of the following sets has the same standard deviation as set {m, n, p, q, r}?

A) {m/2,n/2,p/2,q/2,r/2}
B) { m^2, n^2, p^2, q^2, r^2 }
C) {m + 2, n + 2, p + 2, q + 2, r + 2}
D) {2m,2n,2p,2q,2r}
E) {|m|,|n|,|p|,|q|,|r|}

OA: C


I was wondering when will E be wrong since absolute value will always be positive.

Thanks a lot.

Best Regards,
Sri
Here's another example to show why the correct answer is not E.

If the set is {-1, -1, 1, 1} the Standard Deviation is definitely NOT zero (since the standard deviation is only zero when all of the elements in the set are equal)

For answer choice E, we find the absolute value of each element in the set. When we do so, we get {1, 1, 1, 1}, and the Standard Deviation is definitely zero

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Legendary Member
Posts: 641
Joined: Tue Feb 14, 2012 3:52 pm
Thanked: 11 times
Followed by:8 members

by gmattesttaker2 » Tue Jan 14, 2014 10:01 pm
Uva@90 wrote:
gmattesttaker2 wrote:Hello,

Can you please assist with this:

Which of the following sets has the same standard deviation as set {m, n, p, q, r}?

A) {m/2,n/2,p/2,q/2,r/2}
B) { m^2, n^2, p^2, q^2, r^2 }
C) {m + 2, n + 2, p + 2, q + 2, r + 2}
D) {2m,2n,2p,2q,2r}
E) {|m|,|n|,|p|,|q|,|r|}

OA: C


I was wondering when will E be wrong since absolute value will always be positive.

Thanks a lot.

Best Regards,
Sri
Hi Sri,
The Concept behind this question is,
If we add or subtract a constant to each term in a set Mean will increase or decrease by the same constant SD will not change.

Considering the above statement Answer will be C

Coming to you question
Why Not E?
E option will always be Positive, but set {m, n, p, q, r} may have negative values, as
Let set {2,-2,-1,1} wil not have same SD as {2,2,1,1}

Hope I made it clear.

Earlier even I had same confusion. Later Brent and Mitch had explained me clearly.
Here is the link for the same,
https://www.beatthegmat.com/standard-dev ... tml#701110

Regards,
Uva
Hello Uva,

Thank you very much for the explanation and for sharing the link.

Best Regards,
Sri
Top
Legendary Member
Posts: 641
Joined: Tue Feb 14, 2012 3:52 pm
Thanked: 11 times
Followed by:8 members

by gmattesttaker2 » Tue Jan 14, 2014 10:01 pm
Uva@90 wrote:
gmattesttaker2 wrote:Hello,

Can you please assist with this:

Which of the following sets has the same standard deviation as set {m, n, p, q, r}?

A) {m/2,n/2,p/2,q/2,r/2}
B) { m^2, n^2, p^2, q^2, r^2 }
C) {m + 2, n + 2, p + 2, q + 2, r + 2}
D) {2m,2n,2p,2q,2r}
E) {|m|,|n|,|p|,|q|,|r|}

OA: C


I was wondering when will E be wrong since absolute value will always be positive.

Thanks a lot.

Best Regards,
Sri
Hi Sri,
The Concept behind this question is,
If we add or subtract a constant to each term in a set Mean will increase or decrease by the same constant SD will not change.

Considering the above statement Answer will be C

Coming to you question
Why Not E?
E option will always be Positive, but set {m, n, p, q, r} may have negative values, as
Let set {2,-2,-1,1} wil not have same SD as {2,2,1,1}

Hope I made it clear.

Earlier even I had same confusion. Later Brent and Mitch had explained me clearly.
Here is the link for the same,
https://www.beatthegmat.com/standard-dev ... tml#701110

Regards,
Uva
Hello Uva,

Thank you very much for the explanation and for sharing the link.

Best Regards,
Sri
Top
Post new topic Post Reply
• Page 1 of 1