code: def var(self):
          "Variance"
          n, a, b = self.n, self.a, self.b
          top = n*a*b * (a + b + n)
          btm = (a+b)**2.0 * (a+b+1.0)
          return top / btf var(self):
          "Variance"
          n, a, b = self.n, self.a, self.b
          top = n*a*b * (a + b + n)
          btm = (a+b)**2.0 * (a+b+1.0)
          return top / btm
docs: Variance