Binomial Distribution Function
The binomial distribution, denoted B(n,p), is the distribution
of the total number of successes in n independent trials
when p is the probability of success on each individual trial.
The mean of this distribution is np and the variance is np(1-p).
The above calculates the exact probability that a binomial
variable, B(n,p), is less than or equal to the x-value.
The probability mass function of the B(n,p) distribution is
f(x : n,p) = Cn,x px(1-p)n-x for x =
where Cn,x = n!/(x!(n-x)!) is the number of combinations
of n things taken x at a time. For example, f(0 : 1,.5)=.5