If for a sample of size 60, we have the following information and , then the variance is

If the S.D. of a set of observations is 8 and if each observation is divided by -2, the S.D. of the new set of observations will be

If two variates X and Y are connected by the relation , where a, b, c are constants such that ac < o, then

Let a, b, c, d, e be the observations with mean m and standard deviation s. The standard deviation of the observations a + k, b + k, c + k, d + k, e + k is

The standard deviation of first 10 natural numbers is