The mean deviation about median of the numbers $3 x, 6 x, 9 x, \ldots .81 x$ is 91 , then $|x|=$

$$ \text { The coefficient of variation for the following data is } $$

$$ \begin{array}{llllll} \hline \text { Class interval } & 0-2 & 2-4 & 4-6 & 6-8 & 8-10 \\ \hline \text { Frequency } & 2 & 3 & 5 & 3 & 2 \\ \hline \end{array} $$

The mean deviation from the mean of the discrete data $2,3,5,7,11,13,17,19,22$ is

The probability distribution of a random variable $X$ is given below. Then, the standard deviation of $X$ is

$$ \begin{array}{llllll} \hline \boldsymbol{X}=\boldsymbol{x}_1 & 2 & 3 & 5 & 7 & 12 \\ \hline \boldsymbol{P}\left(\boldsymbol{X}=\boldsymbol{x}_1\right) & 3 k & k & k & 2 k & k \\ \hline \end{array} $$