The mean of $100$ observations is $50$ and their standard deviation is $5$. Then,the sum of squares of all observations is

If the mean of the numbers $a, b, 8, 5, 10$ is $6$ and the variance is $6.80$,then which of the following is a possible value for $a$ and $b$?

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

Let $x_1, x_2, \dots, x_n$ be $n$ observations such that $\sum x_i^2 = 300$ and $\sum x_i = 60$. Which of the following is a possible value for $n$?

For $10$ observations $x_1, x_2, ..., x_{10}$, if $\sum_{i=1}^{10} (x_i + 2)^2 = 180$ and $\sum_{i=1}^{10} (x_i - 1)^2 = 90$, then their standard deviation is:

If the variance of the first $n$ natural numbers is $10$ and the variance of the first $m$ even natural numbers is $16$,then $m + n$ is equal to