The mean deviation from mean of the observations a,a+d,a+2d,…,a+2nd is
n(n+1)d23
n(n+1)2d2
a+n(n+1)d22
None of these
x¯=12n+1[a+(a+d)+…+(a+2nd)]=12n+1[(2n+1)a+d(1+2+…+2n)]=a+d2n2(2n+1)2n+1=a+nd∴MD from mean =12n+1Σxi−x¯=12n+12|d|(1+2+…+n)=n(n+1)|d|(2n+1)