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

 It is currently 16 Dec 2018, 21:07

### 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

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

## Events & Promotions

###### Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### 10 Keys to nail DS and CR questions

December 17, 2018

December 17, 2018

06:00 PM PST

07:00 PM PST

Join our live webinar and learn how to approach Data Sufficiency and Critical Reasoning problems, how to identify the best way to solve each question and what most people do wrong.
• ### FREE Quant Workshop by e-GMAT!

December 16, 2018

December 16, 2018

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

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

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51230
Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

21 Aug 2018, 19:55
00:00

Difficulty:

45% (medium)

Question Stats:

42% (00:40) correct 58% (00:45) wrong based on 43 sessions

### HideShow timer Statistics

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.

_________________
Math Expert
Joined: 02 Aug 2009
Posts: 7108
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

22 Aug 2018, 19:33
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?

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

Hence E
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

##### General Discussion
Manager
Status: Started with mock tests,Kaplan and manhattan score's below
Joined: 11 Jun 2017
Posts: 110
Location: India
GMAT 1: 630 Q44 V33
GMAT 2: 680 Q47 V37
GPA: 3.2
Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

21 Aug 2018, 20:34
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

Director
Joined: 18 Jul 2018
Posts: 502
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

21 Aug 2018, 20:39
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.

Posted from my mobile device
_________________

When you want something, the whole universe conspires in helping you achieve it.

Director
Status: Learning stage
Joined: 01 Oct 2017
Posts: 931
WE: Supply Chain Management (Energy and Utilities)
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

21 Aug 2018, 20:49
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

Director
Status: Learning stage
Joined: 01 Oct 2017
Posts: 931
WE: Supply Chain Management (Energy and Utilities)
Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

### Show Tags

22 Aug 2018, 19:03
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?

_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

Re: Is the standard deviation of set A > standard deviation of set B? &nbs [#permalink] 22 Aug 2018, 19:03
Display posts from previous: Sort by