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SD >2?

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SD >2?

by gmatrant » Sun Aug 08, 2010 3:22 am
Is the standard deviation of numbers w,x,y and z greater than 2?
1) w=3
2) The average of the four numbers is 8
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by gmatmachoman » Sun Aug 08, 2010 3:52 am
Pick C

St 1 : Doesn't give enuf info abt rest of 3 numbers. Insufficient

St 2:
Case 1: 8,8,8,8

SD = 0

case 2 : {-1,17,8,8}

SD is greater than 2.

Inconsistent . Insufficient

Combining st 1 & st 2 :

{3, X,Y, Z}

Case 1 ( Best case scenario) : 3, 13,8, 8 ---- as we need to maintain average of 8

SD = sqrt(12.5) which is certainly greater than 2.

So pick C
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