Let x1,x2,…,xn be n observations such that Σxi2=400 and Σxi=80. Then a possible value of n among the following is
9
12
15
18
Since root mean square ≥ arithmetic mean
∑i=1n xi2n≥∑i=1n xin=400n≥80n⇒n≥16
Hence, the possible value of n is 18.