Author 
Message 
Manager
Joined: 17 Sep 2011
Posts: 161

DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
31 Jan 2012, 02:28
There is a set of consecutive even integers. What is the Standard deviation of the set ? 1)There are 39 elements in the set. 2)The mean of the set is 382. The answer to this question is A. Can someone explain the logic behind this ?
_________________
_________________ Giving +1 kudos is a better way of saying 'Thank You'.



Manager
Status: May The Force Be With Me (DDAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 242
Location: India
Concentration: General Management, Entrepreneurship

Re: DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
31 Jan 2012, 03:10
Hi In order to solve this problem we need to know the mean & the terms of the sample. Statement A : Gives us 39 consecutive even elements Eg : 0,2,4,..... To Compute SD1. Compute the difference of each data point from the mean, and square the result of each 2. compute the average of these values, and take the square root Which we can calculate easily from the given data Thus statement A is sufficient Statement B Mean is 382 only gives us the mid point of the set but not the number of elements hence we cannot calculate the SD Thus statement B is insufficient Hope this helps
_________________
Giving +1 kudos is a better way of saying 'Thank You'.



Manager
Joined: 17 Sep 2011
Posts: 161

Re: DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
31 Jan 2012, 08:19
Thanks man
_________________
_________________ Giving +1 kudos is a better way of saying 'Thank You'.



Senior Manager
Status: Always try to face your worst fear because nothing GOOD comes easy. You must be UNCOMFORTABLE to get to your COMFORT ZONE
Joined: 15 Aug 2014
Posts: 322
Concentration: Marketing, Technology
GMAT 1: 570 Q44 V25 GMAT 2: 600 Q48 V25
WE: Information Technology (Consulting)

DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
09 Apr 2016, 00:20
boomtangboy wrote: Hi
In order to solve this problem we need to know the mean & the terms of the sample.
Statement A : Gives us 39 consecutive even elements Eg : 0,2,4,..... To Compute SD 1. Compute the difference of each data point from the mean, and square the result of each 2. compute the average of these values, and take the square root
Which we can calculate easily from the given data
Thus statement A is sufficient
Statement B Mean is 382 only gives us the mid point of the set but not the number of elements hence we cannot calculate the SD
Thus statement B is insufficient
Hope this helps Dear Experts, Please explain how statement A is sufficient to calculate standard deviation. From the given information which 39 even elements we need to consider . IMO these 39 elements can be from 0,2,4.... or from 100,102,104... will the standard deviation calculated from any of the 'n' number of even integers is same? Please advise
_________________
"When you want to succeed as bad as you want to breathe, then you’ll be successful.”  Eric Thomas
I need to work on timing badly!!



Math Expert
Joined: 02 Aug 2009
Posts: 6514

Re: DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
09 Apr 2016, 00:37
smartguy595 wrote: boomtangboy wrote: Hi
In order to solve this problem we need to know the mean & the terms of the sample.
Statement A : Gives us 39 consecutive even elements Eg : 0,2,4,..... To Compute SD 1. Compute the difference of each data point from the mean, and square the result of each 2. compute the average of these values, and take the square root
Which we can calculate easily from the given data
Thus statement A is sufficient
Statement B Mean is 382 only gives us the mid point of the set but not the number of elements hence we cannot calculate the SD
Thus statement B is insufficient
Hope this helps Dear Experts, Please explain how statement A is sufficient to calculate standard deviation. From the given information which 39 even elements we need to consider . IMO these 39 elements can be from 0,2,4.... or from 100,102,104... will the standard deviation calculated from any of the 'n' number of even integers is same? Please advise hi, since the elments are consecutive and number of elements are same, SD will remain same.. For SD we take out AVERAGE and subtract each number from it... two cases 1) 0,2,4....38*2 average = 19*2 = 38.. subtract ecah number 380 = 38 and 382 = 36 and so on 2) 100,102.... 100+38*2 average = 100+19*2 = 138 Difference 138100=38 and 1362 = 36.. so you see the difference is the same.. SD depend s on HOW far the numbers are SPREAD.. and in each case with 39 consecutive elements, the numbers are equally spread Hope it helps
_________________
1) Absolute modulus : http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effectsofarithmeticoperationsonfractions269413.html
GMAT online Tutor



Senior Manager
Status: Always try to face your worst fear because nothing GOOD comes easy. You must be UNCOMFORTABLE to get to your COMFORT ZONE
Joined: 15 Aug 2014
Posts: 322
Concentration: Marketing, Technology
GMAT 1: 570 Q44 V25 GMAT 2: 600 Q48 V25
WE: Information Technology (Consulting)

Re: DS Q There is set of consecutive even integers. What is S.D?
[#permalink]
Show Tags
09 Apr 2016, 07:01
chetan2u wrote: smartguy595 wrote: boomtangboy wrote: Hi
In order to solve this problem we need to know the mean & the terms of the sample.
Statement A : Gives us 39 consecutive even elements Eg : 0,2,4,..... To Compute SD 1. Compute the difference of each data point from the mean, and square the result of each 2. compute the average of these values, and take the square root
Which we can calculate easily from the given data
Thus statement A is sufficient
Statement B Mean is 382 only gives us the mid point of the set but not the number of elements hence we cannot calculate the SD
Thus statement B is insufficient
Hope this helps Dear Experts, Please explain how statement A is sufficient to calculate standard deviation. From the given information which 39 even elements we need to consider . IMO these 39 elements can be from 0,2,4.... or from 100,102,104... will the standard deviation calculated from any of the 'n' number of even integers is same? Please advise hi, since the elments are consecutive and number of elements are same, SD will remain same.. For SD we take out AVERAGE and subtract each number from it... two cases 1) 0,2,4....38*2 average = 19*2 = 38.. subtract ecah number 380 = 38 and 382 = 36 and so on 2) 100,102.... 100+38*2 average = 100+19*2 = 138 Difference 138100=38 and 1362 = 36.. so you see the difference is the same.. SD depend s on HOW far the numbers are SPREAD.. and in each case with 39 consecutive elements, the numbers are equally spread Hope it helps Thanks for the explanation chetan2u
_________________
"When you want to succeed as bad as you want to breathe, then you’ll be successful.”  Eric Thomas
I need to work on timing badly!!




Re: DS Q There is set of consecutive even integers. What is S.D? &nbs
[#permalink]
09 Apr 2016, 07:01






