[a,a+d,a+2d,......,a+2nd],[" -ilicels "]

The variance of series a,a+d,a+2d,.........,a+2nd is

Mean deviation of the series a,a+d,a+2d,......,a+2nd from its mean is (a) ((n+1)d)/((2n+1))( b )(nd)/(2n+1) (c) ((2n+1)d)/(n(n+1)) (d) (n(n+1)d)/(2n+1)

The mean deviation of the series a , a+d , a+2d ,.....,a+2nd from its mean is (a) ((n+1)d)/(2n+1) (b) (n d)/(2n+1) (c) (n(n+1)d)/(2n+1) (d) ((2n+1)d)/(n(n+1))

For the arithmetic progression a,(a+d),(a+2d),(a+3d),......,(a+2nd) , the mean deviation from mean is

The mean of the series a, a + d, a + 2d, …, a + 2 nd, is

M.D for the observations a,a +d,a +2d, ……., a +2nd is

The mean deviation from mean of the observations a, a + d, a + 2d,… a + 2 nd is :