@Test
public void testOffset() {

  OnlineSummarizer s = new OnlineSummarizer();
  Sampler<Double> sampler = new Normal(2, 5);
  for (int i = 0; i < 10001; i++) {
    s.add(sampler.sample());
  }
  assertEquals(String.format("m = %.3f, sd = %.3f", s.getMean(), s.getSD()), 2, s.getMean(), 0.04 * s.getSD());
  assertEquals(5, s.getSD(), 0.12);
}