There are $800$ families with four children in each family. Assuming an equal chance for every child to be a boy or a girl,the number of families expected to have children of both sexes is:

In a tournament,a team plays $10$ matches with probabilities of winning and losing each match as $\frac{1}{3}$ and $\frac{2}{3}$ respectively. Let $x$ be the number of matches that the team wins,and $y$ be the number of matches that the team loses. If the probability $P(|x-y| \leq 2)$ is $p$,then $3^9 p$ equals....................

$A$ fair coin is tossed $n$ times. If the probability that head occurs $6$ times is equal to the probability that head occurs $8$ times,then $n$ is equal to:

In a Binomial distribution with $n=4$,if $2 P(X=3)=3 P(X=2)$,then the variance is

$A$ coin is tossed $100$ times. What is the probability of getting a tail an odd number of times?

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