X is a random variable with binomial distribution
The probabilty of getting n heads out of N trials with a coin that has probabilty p of coming up heads (and probabilty q=1p of getting tails) is
(N,n)*p^{n}q^{Nn} = N!/n!(Nn)! * p^{n}(1p)^{Nn}
where (N,n) is a binomial coefficient
the standard deviation is Sqrt[N*p*(1p)]
Sorry if I gave too much away
