$A$ die is thrown twice. If getting a number greater than $4$ on the die is considered a success,then the variance of the probability distribution of the number of successes is

The centers for disease control have determined that when a person is given a vaccine, the probability that the person will develop immunity to a virus is $0.8$. If $8$ people are given this vaccine, then the probability that exactly $4$ will develop immunity is...

The probability of a shooter hitting a target is $\frac{3}{4}$. What is the minimum number of times he/she must fire so that the probability of hitting the target at least once is greater than $0.99$?

In a binomial distribution $B(n, p)$,the sum and product of the mean and variance are $5$ and $6$ respectively. Find the value of $6(n+p-q)$.

Two dice are thrown simultaneously. If $X$ denotes the number of sixes,then the expectation of $X$ is

An experiment succeeds twice as often as it fails. Find the probability that in the next six trials,there will be at least $4$ successes.