If $X \sim B\left(8, \frac{1}{2}\right)$,then $P(|X-4| \leq 2) = $

$A$ manufacturer of locks knows that $2 \%$ of his product is defective. If he sells the locks in boxes each with $100$ locks and guarantees that not more than $2$ locks will be defective in a box,then the probability that a box will fail to meet the guaranteed quality is

Ten bulbs are drawn successively,with replacement,from a lot containing $10 \%$ defective bulbs. The probability that there is at least one defective bulb is:

If the mean and variance of a binomial distribution are $4$ and $2$ respectively,then the probability of getting $2$ successes is:

An unbiased coin is tossed to get $2$ points for turning up a head and $1$ point for the tail. If three unbiased coins are tossed simultaneously, then the probability of getting a total of an odd number of points is

If a random variable $X$ follows the Binomial distribution $B(33, p)$ such that $3P(X=0) = P(X=1)$,then the value of $\frac{P(X=15)}{P(X=18)} - \frac{P(X=16)}{P(X=17)}$ is equal to