def test_factorial_moment(): X = Poisson('X', 2) Y = Binomial('Y', 2, S.Half) Z = Hypergeometric('Z', 4, 2, 2) assert factorial_moment(X, 2) == 4 assert factorial_moment(Y, 2) == S.Half assert factorial_moment(Z, 2) == Rational(1, 3) x, y, z, l = symbols('x y z l') Y = Binomial('Y', 2, y) Z = Hypergeometric('Z', 10, 2, 3) assert factorial_moment(Y, l) == y**2*FallingFactorial( 2, l) + 2*y*(1 - y)*FallingFactorial(1, l) + (1 - y)**2*\ FallingFactorial(0, l) assert factorial_moment(Z, l) == 7*FallingFactorial(0, l)/\ 15 + 7*FallingFactorial(1, l)/15 + FallingFactorial(2, l)/15
def test_factorial_moment(): X = Poisson("X", 2) Y = Binomial("Y", 2, S.Half) Z = Hypergeometric("Z", 4, 2, 2) assert factorial_moment(X, 2) == 4 assert factorial_moment(Y, 2) == S.Half assert factorial_moment(Z, 2) == Rational(1, 3) x, y, z, l = symbols("x y z l") Y = Binomial("Y", 2, y) Z = Hypergeometric("Z", 10, 2, 3) assert factorial_moment(Y, l) == y ** 2 * FallingFactorial(2, l) + 2 * y * ( 1 - y ) * FallingFactorial(1, l) + (1 - y) ** 2 * FallingFactorial(0, l) assert ( factorial_moment(Z, l) == 7 * FallingFactorial(0, l) / 15 + 7 * FallingFactorial(1, l) / 15 + FallingFactorial(2, l) / 15 )