If the first item is increased by 1, second by 2 and so on, then the new mean is
X¯+n
X¯+n2
X¯+n+12
none of these
Let x1,x2,…,xn be n values of variable X. Then
X¯=1nΣxi
Let y1=x1+1,y2=x2+2,y3=x3+3,…,yn=xn+n Then the mean of the new series is given by
X′¯=1n∑yi⇒ X′¯=1n∑i xi+i⇒ X′¯=1n∑i xi+1n(1+2+3+…+n)⇒ X′¯=X¯+1n⋅n(n+1)2=X¯+n+12