If arithmetic mean of 9 observations is 100 and that of 6 is 80 .Then the combined mean of all the 15 observations will be

if the randon error in the arithmetic mean of 50 observations is alpha , then the random error in the arithmetic mean of 150 observations would be

The mean of 5 observations is 60, the mean of 10 observations is 30 and the mean of 15 observations is 20. The mean of all the 30 observations is (a)20quad (b) 25quad (c) 30 (d) 40

The random error in the arithmetic mean of 100 observations is x, then random error in the arithmetic mean of 400 observations would be

If the mean of five observations is 11, find the mean of first three observations.

The arithmetic mean of 11 observations is 11. The arithmetic mean of the first 6 observations is 10.5 and the arithmetic mean of the last 6 observations is 11.5. What is the sixth observation ?

The mean of 20 observations is 30. If the mean of first 15 observations is 32, find the mean of last 5 observations.

If the mean of 100 observations is 50 and their standard deviations is 5,than the sum of all squares of all the observations is

Let p be the mean of m observations and q be the mean of n observations, where p lt q . If the combined mean of (m + n) observations is c, then which one of the following is correct?