@Override
    public double rand() {
        if (gaussian == null) {
            gaussian = new GaussianDistribution(mu, sigma);
        }

        return Math.exp(gaussian.rand());
    }
@Test
    public void testSd() {
        System.out.println("sd");
        LogNormalDistribution instance = new LogNormalDistribution(1.0, 1.0);
        instance.rand();
        assertEquals(5.874744, instance.sd(), 1E-6);
    }