'Check statistical properties of output.'

def check_output(self, out):

    expected_avg = (1 << 31)
    expected_std = ((1 << 32) / np.sqrt(12))
    rtol = 0.05
    np.testing.assert_allclose(out.mean(), expected_avg, rtol=rtol)
    np.testing.assert_allclose(out.std(), expected_std, rtol=rtol)
