SD is measure of the variations of the elements of set with respect to mean.
Lets say water tanks have
10 , 20 , 30, 40, 50 , 60 gallons
Now after removing 30% from each we have
As all elements are reduced by 30%, the mean will also be reduced by 30%. So the variation of elements with respect to the new mean is also same. So SD will remain the same.
statement 2 don't tell the scenario after the removal. So its INSUFF.
SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008