$A$ coin is tossed $4$ times. The probability that at least one head turns up is

When success is not an impossible event,then the mean of Binomial distribution is

If the probability of hitting a target by a shooter,in any shot,is $\frac{1}{3}$,then the minimum number of independent shots at the target required by him so that the probability of hitting the target at least once is greater than $\frac{5}{6}$,is

If the mean and variance of a binomial variate $X$ are $8$ and $4$ respectively,then $P(X < 3)$ equals to

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 $0.99$?

An urn contains $25$ balls of which $10$ balls bear a mark $'X'$ and the remaining $15$ bear a mark $'Y'$. $A$ ball is drawn at random from the urn,its mark is noted down and it is replaced. If $6$ balls are drawn in this way,find the probability that not more than $2$ will bear $'Y'$ mark.