Let $O$ be the mean deviation of the first five odd natural numbers about their mean and $P$ be the mean deviation of the first five prime numbers about their mean. Then $P-O=$

The mean deviation from the mean of the discrete data $1, 3, 4, 7, 11, 18, 29, 47, 78$ is

Find the mean deviation about the median of the following distribution:
$ \begin{array}{|l|l|l|l|l|l|} \hline \text{Marks obtained} & 10 & 11 & 12 & 14 & 15 \\ \hline \text{Number of students} & 2 & 3 & 8 & 3 & 4 \\ \hline \end{array} $

The mean deviation about the median of the following distribution is:

$x$	$6$	$12$	$18$	$24$	$30$	$36$	$42$
$f$	$4$	$7$	$9$	$18$	$15$	$10$	$5$

In a series of $3n$ observations,if $n$ observations are equal to $a$ and the remaining $2n$ observations are equal to $-2a$,then the mean deviation of the observations about their mean is:

The mean deviation about the mean for the data $4, 7, 8, 9, 10, 12, 13, 17$ is