If $M.D.$ is $12$,the value of $S.D.$ will be

If the mean of $10$ observations is $50$ and the sum of the squares of the deviations of the observations from the mean is $250$,then the coefficient of variation of those observations is

The standard deviation of the scores $505, 510, 515, 520, \ldots, 595$ is

The sum of $10$ values is $12$ and the sum of their squares is $16.9$,then their standard deviation $(S.D.)$ is

For the following frequency distribution,find the variance:

$X$	$5$	$6$	$7$	$8$	$10$
Frequency	$3$	$7$	$4$	$2$	$4$

Find the variance and standard deviation for the following data:

$x_i$	$4$	$8$	$11$	$17$	$20$	$24$	$32$
$f_i$	$3$	$5$	$9$	$5$	$4$	$3$	$1$