The greatest value of a collection of data is $72$ and the least value is $28$. Then the coefficient of range is.

Two sets each of $20$ observations, have the same standard deviation $'5'$. The first set has a mean $'17'$ and the second set mean $'22'$ then standard deviation of the combining the given two sets is

In a series of $100$ observations, half of them is equal to $p$ and remaining half equal to $-p$ if the standard deviation of these observations is $10$ then $|p|=$__   

The mean and standard deviation of $1,2,3,4,5,6$ are 

Ina a class of 20 students, each student can score 10 or 0 marks in a certain examination. The maximum possible variance in the marks of the students in the class is