If the mean deviation of $5$ observations about the mean $3$ is $1.2$,find the coefficient of mean deviation.

Calculate the mean deviation about the mean of the set of first $n$ natural numbers when $n$ is an even number.

Find the mean deviation about the median for the following data:

Marks	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$
No of Girls	$6$	$8$	$14$	$16$	$4$	$2$

Consider the following distribution:

$x_i$	$2$	$4$	$6$	$8$	$10$
$f_i$	$1$	$2$	$3$	$2$	$1$

The sum of the mean deviation from the mean and the mean deviation from the median of this distribution is:

Let $S$ be the set of all values of $a_1$ for which the mean deviation about the mean of $100$ consecutive positive integers $a_1, a_2, a_3, \ldots, a_{100}$ is $25$. Then $S$ is

Let $\bar{X}$ and $M.D.$ be the mean and the mean deviation about $\bar{X}$ of $n$ observations $x_i,$ $i = 1, 2, \dots, n.$ If each of the observations is increased by $5,$ then the new mean and the mean deviation about the new mean,respectively,are