In a series of `2n` observations, half of them equal `a` end remaining half equal `-a.` If the S.D. of the observationsis `2,` then `|a|` equals (1) `1/n` (2) `sqrt2` (3) `2` (4) `sqrt2/n`

In a series of 2n observations,half of them equal a end remaining half equal -a. If the S.D.of the observationsis 2, then |a| equals (1) (1)/(n) (2) sqrt(2)(3)2(4)(sqrt(2))/(n)

In a series of 2n observations, half of them are equal to a^(2) and the remaining half are equal to -a^(2) . If the standard deviation of the observation is 2, then |a| is equal to

Let in a series of 2n observations, half of them are equal to a and remaining half are equal to -a. Also by adding a b in each of these observation, the mean and standard deviation of a new set become 5 and 20 respectively. Then the value of a^2+b^2 is equal to :

In a series of 20 observations 10 observation each equal to k and each of the remaining half is equal to -k .If the standard deviation of the observations is 2, then write the value of k

If the observation 1, 2, 3, ……….., n occur with frequency, n,(n-1), (n-2),…..,1 respectively such that the mean of observations is (13)/(3) , then n is equal to

If tantheta+sintheta=m and tantheta-sintheta=n , then the value of m^2-n^2 is equal to (a)4 mn (b) 2sqrt(mn) (c) 4sqrt(mn) (d) 2sqrt(m//n)

Two radioactive substances X and Y originally have N_(1) and N_(2) nuclei respectively. Half life of X is half of the half life of Y. After three half lives of Y, number of nuclei of both are equal. (N_(1))/(N_(2)) The ratio N will be equal to :