The mean and variance of a binomial distribution are 4 and 2 respectively. Then the probability of exactly two successes is

Mean of n observations x₁, x₂, ...., x_n is $$\overline x $$. If an observation x_q is replaced by x_q' then the new mean is

Standard deviation of n observations a₁, a₂, a₃, ....., a_n is $$\sigma$$. Then, the standard deviation of the observations $$\lambda$$a₁, $$\lambda$$a₂, ....., $$\lambda$$a_n is