If 9∑i=1(xi−5)=9 and 9∑i=1(xi−5)2=45, then the standard deviation of the 9 items x1,x2,.....,x9 is
If ∑18i=1(xi−8)=9 and ∑18i=1(xi−8)2=45 then the standard deviation of x1,x2,…..x18 is