is the standard deviation of number w,x,y,z greater than 2 : DS Archive
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 16 Jan 2017, 23:55

### 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 June
Open Detailed Calendar

# is the standard deviation of number w,x,y,z greater than 2

Author Message
Senior Manager
Joined: 29 Aug 2005
Posts: 283
Followers: 2

Kudos [?]: 51 [1] , given: 0

is the standard deviation of number w,x,y,z greater than 2 [#permalink]

### Show Tags

10 Jun 2008, 22:07
1
KUDOS
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

is the standard deviation of number w,x,y,z greater than 2
(1) w =3
(2) the average of four numbers is 8

analysing statement 1

value of x, y,z are not defined hence this statement is insufficent

analysing statement 2

we are given that average of 4 numbers is 8
but again we do not know the individual values for the variables w,x,y,z

therefore statement 2 is insufficent

together both statements put together
we get

w=3
average of four numbers is 8, but we still do not know the values of x,y and z

so we cant arrive at the standard deviation of these 4 numbers

IMO E should be the answer (which needless to say is different from what the OA is)

am i missing something in this question
_________________

The world is continuous, but the mind is discrete

Senior Manager
Joined: 19 Apr 2008
Posts: 320
Followers: 3

Kudos [?]: 78 [1] , given: 0

### Show Tags

10 Jun 2008, 22:34
1
KUDOS
vdhawan1 wrote:
is the standard deviation of number w,x,y,z greater than 2
(1) w =3
(2) the average of four numbers is 8

analysing statement 1

value of x, y,z are not defined hence this statement is insufficent

analysing statement 2

we are given that average of 4 numbers is 8
but again we do not know the individual values for the variables w,x,y,z

therefore statement 2 is insufficent

together both statements put together
we get

w=3
average of four numbers is 8, but we still do not know the values of x,y and z

so we cant arrive at the standard deviation of these 4 numbers

IMO E should be the answer (which needless to say is different from what the OA is)

am i missing something in this question

ANS C .

1 and 2 alone not sufficient

if you combine both the statement: W=3 , now choose other three numbers closely clustered such that avg of W, X, Y,Z is 8 . Such data set is {3 , 9 , 9 ,10} , SD of which is > 2 , hence SD of any other combination will also be > 2 .
Director
Joined: 27 May 2008
Posts: 549
Followers: 8

Kudos [?]: 312 [1] , given: 0

### Show Tags

10 Jun 2008, 22:37
1
KUDOS
standard deviation SD tell us how far / close numbers are from the mean.

if SD is low, means numbers are closer to mean.

Combinig the two statements, we have w = 3 and mean = 8.
Lets consider an example set where the numbers are closest to the mean, including w = 3. This set will be - 3,8,8,13.
now we can calculate SD for this set. It'll be sqrt((5^2+0^2+0^2+5^2)/4) = sqrt(12.5) which is more than 2.

Any other combination, SD will be more than this.

Senior Manager
Joined: 29 Aug 2005
Posts: 283
Followers: 2

Kudos [?]: 51 [0], given: 0

### Show Tags

10 Jun 2008, 22:56
durgesh79 wrote:
standard deviation SD tell us how far / close numbers are from the mean.

if SD is low, means numbers are closer to mean.

Combinig the two statements, we have w = 3 and mean = 8.
Lets consider an example set where the numbers are closest to the mean, including w = 3. This set will be - 3,8,8,13.
now we can calculate SD for this set. It'll be sqrt((5^2+0^2+0^2+5^2)/4) = sqrt(12.5) which is more than 2.

Any other combination, SD will be more than this.

Ok guys got the point
thanks for the help
_________________

The world is continuous, but the mind is discrete

Re: DS question   [#permalink] 10 Jun 2008, 22:56
Display posts from previous: Sort by