Two sample of size 100 and 150 respectively have means 15 and 16 and standard deviations 3 and 4 respectively. Find the combined mean and standard deviation of Size 250.

Find the mean , variance and standard deviation :

Two sample of size 100 and 150 respectively have means 50 and 60 deviation of the combined sample of size 250.

The mean and standard deviation of two numbers are 10 and 2 respectively. Find the numbers.

For a group containing 100 observations, the arithmetic mean and standard deviation are 8 and sqrt(10.5) . For 50 observations selected from the 100 observations, the arithmetic mean and standard deviations are 10 and 2 respectively. Find the arithmetic mean and the standard deviation of the other half.

The means of two samples of sizes 10 and 20 respectively are 24 and 45 and the standard deviations are 6 and 11. Obtain the standard deviation of the sample of size 30 obtained by combining the two samples. (sqrt19067=138)

If the first sample A of 100 items has the mean 15 and standard deviation 3 and second sample B has 150 items. If the combined mean and standard deviation of itmes of both the sample is 15.6 and sqrt(13.44) then then standard deviation of items of sample B is