For a frequency distribution,the $7^{th}$ decile is computed by the formula:

The mean and $S.D.$ of the marks of $200$ candidates were found to be $40$ and $15$ respectively. Later,it was discovered that a score of $40$ was wrongly read as $50$. The correct mean and $S.D.$ respectively are...

If the mean and variance of six observations $7, 10, 11, 15, a, b$ are $10$ and $\frac{20}{3}$ respectively,then the value of $|a-b|$ is equal to:

The mean and variance of seven observations are $8$ and $16$ respectively. If five of the observations are $2, 4, 10, 12, 14$,then the product of the remaining two observations is:

If the mean and variance of eight numbers $3, 7, 9, 12, 13, 20, x$,and $y$ are $10$ and $25$ respectively,then $x \cdot y$ is equal to

Let $x_1, x_2, \ldots, x_{11}$ be the observations satisfying $\sum_{i=1}^{11}(x_i-4)=22$ and $\sum_{i=1}^{11}(x_i-4)^2=154$. If the mean and variance of the observations are $\alpha$ and $\beta$,then the quadratic equation having the roots $\frac{\alpha}{\beta}$ and $\frac{\beta}{\alpha}$ is