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

Let the mean and the standard deviation of the observations $2, 3, 3, 4, 5, 7, a, b$ be $4$ and $\sqrt{2}$ respectively. Then the mean deviation about the mode of these observations is:

If $a_0, a_1, \ldots, a_{11}$ are in an arithmetic progression with common difference $d$,then their mean deviation from their arithmetic mean is

The mean deviation about the median is $..........$

If the mean deviation of the data $1, 1+d, 1+2d, \ldots, 1+100d$ $(d > 0)$ from their mean is $255$,then $d$ is equal to:

If the mean deviation about the median of $x, 2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x, 10x$ is $30$,then $|x|$ equals: