The following data represents the frequency distribution of $20$ observations.

$x_i$	$3$	$4$	$5$	$8$	$10$	$11$
$f_i$	$\alpha+2$	$(\alpha-1)^2$	$4$	$\alpha-1$	$2$	$\alpha$

Then its mean deviation about the mean is

If the mean deviation about the median of the numbers $a, 2a, 3a, \dots, 50a$ is $50$,then what is the value of $|a|$?

If $10$ is the mean of the data $2, 3, 5, 18, 17, 15, 13, x, 9, 7$,then the mean deviation of this data about its mean is

$\begin{aligned} &\text{Find the mean deviation about the mean for the following data:} \\ &\begin{array}{|l|c|c|c|c|c|} \hline \text{Class Interval} & 0-6 & 6-12 & 12-18 & 18-24 & 24-30 \\ \hline \text{Frequency} & 1 & 2 & 3 & 2 & 1 \\ \hline \end{array} \end{aligned}$

If the mean of $4, 7, 2, 8, 6$ and $a$ is $7$,find the mean deviation about the median of these observations.

If the mean of $4, 7, 2, 8, 6$ and $a$ is $7$,then the mean deviation from the median of these observations is