In a series of $2n$ observations, half of them equal to $a$ and remaining half equal to $-a$. If the standard deviation of the observations is $2$, then $|a|$ equals
$\frac{{\sqrt 2 }}{n}$
$\sqrt 2 $
$2$
$\frac{1}{n}$
The $S.D.$ of $5$ scores $1, 2, 3, 4, 5$ is
In any discrete series (when all values are not same) the relationship between $M.D.$ about mean and $S.D.$ is
Mean of $5$ observations is $7.$ If four of these observations are $6, 7, 8, 10$ and one is missing then the variance of all the five observations is
The variance $\sigma^2$ of the data is $ . . . . . .$
$x_i$ | $0$ | $1$ | $5$ | $6$ | $10$ | $12$ | $17$ |
$f_i$ | $3$ | $2$ | $3$ | $2$ | $6$ | $3$ | $3$ |
The sum of squares of deviations for $10$ observations taken from mean $50$ is $250$. The co-efficient of variation is.....$\%$