The mean deviation from the mean of the data given below is

$\text{Marks}$	$10$	$15$	$20$	$25$	$30$
$\text{Number of students}$	$2$	$4$	$6$	$8$	$5$

The mean deviation about the mean of the following data is nearly:

Size $(x)$	$1$	$3$	$5$	$7$	$9$	$11$	$13$	$15$
Frequency $(f)$	$3$	$3$	$4$	$14$	$7$	$4$	$3$	$4$

The mean deviation of the numbers $a, a+d, a+2d, \ldots, a+2nd$ from their mean is equal to

The mean deviation from the median for the following data is

$x_i$	$2, 9, 8, 3, 5, 7$
$f_i$	$5, 3, 1, 6, 6, 1$

The mean and variance of $10$ observations are $9$ and $34.2$,respectively. If $8$ of these observations are $2, 3, 5, 10, 11, 13, 15, 21$,then the mean deviation about the median of all the $10$ observations is

If the mean deviation about the median of the numbers $a, 2a, 3a, \dots, 50a$ is $50$,then $|a|$ equals: