The $S.D.$ of $5$ scores $1, 2, 3, 4, 5$ is

If the total number of observations is $n = 20$,$\sum x_i = 1000$ and $\sum x_i^2 = 84000$,then the variance of the distribution is

The variance is independent of the change of which of the following?

Let $X = \{x \in N : 1 \leq x \leq 17\}$ and $Y = \{ax + b : x \in X \text{ and } a, b \in R, a > 0\}$. If the mean and variance of the elements of $Y$ are $17$ and $216$ respectively,then $a + b$ is equal to:

The variance of the first $50$ even natural numbers is

Find the coefficient of variation for the given observations: $10, 14, 11, 9, 8, 12, 6$. (in $\%$)