Binomial Distribution

gistfile1.txt

def factorial(n)
  (2..n).inject(1) { |o,k| o * k }
end

def binomial_coefficient(n,k)
  factorial(n) / (factorial(n - k) * factorial(k))
end

def binomial_distribution(p,n)
  (1..n).inject(0) do |total,k|
    total + binomial_coefficient(n,k) * ((p ** k) * ((1 - p) ** (n - k)))
  end
end