Express standard deviation of the composite group in terms of number of observations, arithmetic means and variances of two groups.

Write two numbers with mean 10 and variance 4.

The standard deviation of first 10 natural numbers is

Find two numbers whose arithmetic mean is 34 and the geometric mean is 16.

Standard deviation of first 10 natural numbers is

Show that the sum of deviations of a set of observations about their mean is Zero.

Halogens belong to the group number

Let sigma be the standard deviation of n observations. Each of the n observation is multiplied by a constant c. Then the standard deviation of the resulting numbers is

The arithmetic mean and standard deviation of 7 observations are respectively 8 and 4.If five of the observations are 2,4,10,12 and 14 then find the values of the remaining two

The mean and standard deviation of a group of 100 observations were found to be 20 and 3, respectively. Later on it was found that three observations were incorrect, which were recorded as 21, 21 and 18. Find the mean and standard deviation if the incorrect observations are omitted.

Find that mean deviation from Arithmetic mean of the' natural numbers from 1 to 5