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

If the mean and standard deviation of 5,3,7,a,b are 5 and 2 respectively, then a and b are roots of equation.

A simple of 25 variates has mean 40 and standard deviation 5 and a second sample of 35 variates has mean 45 and the standard deviation 2. Find the mean and standard deviation of the two samples of variates , taken together.

The mean and standard deviation for a,b and 2 are 3 and 1 respectively,then value of ab is

If the standard deviation of 1,2,3,4.......10 is sigma , then find the standard deviation of 11, 12,13,14,.....,20.

If the mean and the standard deviation of the data 3,5,7,a,b are 5 and 2 respectively, then a and b are the roots of the equation :

If the mean and standard deviation of 5 observations x_(1),x_(2),x_(3),x_(4),x_(5) are 10 and 3 respectively,then the variance of 6 observations x_(1),x_(2),x_(3),x_(4),x_(5) and 50 is equal to