If the mean and standard deviation of a binomial distribution are $20$ and $4$,respectively,then the number of trials is $.......$

If $X$ and $Y$ are two independent binomial variates,satisfying $B(10, 1/2)$ and $B(8, 1/2)$ respectively,then the probability $P(X + Y = 2)$ is

If the mean and the variance of a Binomial variate $X$ are $2$ and $1$ respectively,then the probability that $X$ takes a value greater than $1$ is equal to

An unbiased coin is tossed $8$ times. The probability of obtaining at least one head and at least one tail is

Let a random variable $X$ have a Binomial distribution with mean $8$ and variance $4$. If $P(X \leq 2) = \frac{K}{2^{16}}$,then $K$ is

The mean and variance of a binomial variable $X$ are $2$ and $1$ respectively. Then,the probability that $X$ takes values greater than $1$ is