If the algebraic sum of deviations of $20$ observations from $30$ is $20$,then the mean of the observations is:

The range of the data $35, 12, 21, 24, 15, 7, 16, 12, 30, 32, 13, 17$ is

The total expenditure incurred by an industry under different heads is best presented as a

The mean of five observations is $4$ and their variance is also $4$. If three of the five observations are $1, 3, 4$,then the product of the other two is:

The mean and standard deviation of $15$ observations were found to be $12$ and $3$ respectively. On rechecking,it was found that an observation was read as $10$ in place of $12$. If $\mu$ and $\sigma^2$ denote the mean and variance of the correct observations respectively,then $15(\mu+\mu^2+\sigma^2)$ is equal to $...................$

The number of values of $a \in N$ such that the variance of $3, 7, 12, a, 43-a$ is a natural number is (Mean $= 13$).