GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 23 Oct 2019, 11:13

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

Is the standard deviation of set A > standard deviation of set B?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58464
Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 21 Aug 2018, 20:55
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

42% (00:56) correct 58% (00:52) wrong based on 79 sessions

HideShow timer Statistics

Most Helpful Expert Reply
Math Expert
avatar
V
Joined: 02 Aug 2009
Posts: 8023
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 22 Aug 2018, 20:33
PKN wrote:
PKN wrote:
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)


Hi chetan2u,
Could you please guide me where I am wrong in my explanation above?

Thanking you in advance.



Hi..

You have gone wrong in taking number of elements of each.

Combined..
Set A consists of consecutive multiple of 10, say 10,20
Set B = {2,4,6}
SD of A> SD of B..

But if set A={10,20}
And set B = {2,4,6,8,10,........50}
SD of A<SD of B

Different answers possible..
Hence E
_________________
General Discussion
Manager
Manager
User avatar
G
Status: In last prep stage
Joined: 11 Jun 2017
Posts: 157
GMAT 1: 630 Q44 V33
GMAT 2: 680 Q47 V37
GPA: 3.2
Premium Member
Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 21 Aug 2018, 21:34
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.



Standard deviation is 0,if all elements are equal.
Also Std deviation is always greater than or equal to zero.
Since by one std deviation we cannot tell for sure if it is less or greater than other deviation,both statements are required.

Ans :C
_________________
Thanks,
Ankit
Target Score:730+

If the post was useful,please send the kudos
NUS School Moderator
avatar
V
Joined: 18 Jul 2018
Posts: 1020
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Reviews Badge
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 21 Aug 2018, 21:39
Statement 1 doesn't give any info about Set B. Hence insufficient.
Statement 2 doesn't give any info about Set A. Hence insufficient.

Combining both we can say that SD of A will always be greater than B.Irrespective of the number of elements in each set.

C is the answer.

Posted from my mobile device
_________________
Press +1 Kudos If my post helps!
VP
VP
User avatar
D
Status: Learning stage
Joined: 01 Oct 2017
Posts: 1011
WE: Supply Chain Management (Energy and Utilities)
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 21 Aug 2018, 21:49
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)
_________________
Regards,

PKN

Rise above the storm, you will find the sunshine
VP
VP
User avatar
D
Status: Learning stage
Joined: 01 Oct 2017
Posts: 1011
WE: Supply Chain Management (Energy and Utilities)
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

Show Tags

New post 22 Aug 2018, 20:03
PKN wrote:
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)


Hi chetan2u,
Could you please guide me where I am wrong in my explanation above?

Thanking you in advance.
_________________
Regards,

PKN

Rise above the storm, you will find the sunshine
Intern
Intern
avatar
B
Joined: 07 Apr 2019
Posts: 6
Standard deviation of two different sets based on number of elements  [#permalink]

Show Tags

New post 18 Sep 2019, 04:26
Hi Experts I came across a statement in a gmat prep material. Tried number picking and checked; I'm not quite convinced.
Seeking experts' opinion: GMATNinja Bunuel VeritasKarishma

The statement goes: "Since standard deviation is a measure of dispersion around the mean, the number of terms is a hugely important piece of information.
If set B had a million consecutive multiples of 2, it would clearly have a greater standard deviation than set A if it only contained 10 consecutive multiples of 10."

The question : " Is the standard deviation of set A > standard deviation of set B?
(1) Set A consists of consecutive multiples of 10.
(2) Set B consists of consecutive multiples of 2.
GMAT Club Bot
Standard deviation of two different sets based on number of elements   [#permalink] 18 Sep 2019, 04:26
Display posts from previous: Sort by

Is the standard deviation of set A > standard deviation of set B?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne