@Test
  public void testConstructors() {
    VariableStatistics vs1 = new VariableStatistics();
    Assert.assertEquals(vs1.getCount(), 0);
    Assert.assertEquals(vs1.getSum(), 0, TOLERANCE);
    Assert.assertEquals(vs1.getSumSquares(), 0, TOLERANCE);

    VariableStatistics set1 = getVS1();
    VariableStatistics set2 = getVS1();
    Assert.assertTrue(set1.equivalent(set2));
    Assert.assertFalse(set1.equivalent(vs1));

    Assert.assertEquals(set1.getCount(), DATA_SET_SIZE);
    Assert.assertEquals(set1.getSum(), 30, TOLERANCE);
    Assert.assertEquals(set1.getSumSquares(), 166, TOLERANCE);
    Assert.assertEquals(set1.getMean(), 5, TOLERANCE);
    double stdev = set1.getStandardDeviation();
    Assert.assertEquals(stdev, 1.63299, TOLERANCE);

    set2 = getVS2();
    Assert.assertEquals(set2.getCount(), DATA_SET_SIZE);
    Assert.assertEquals(set2.getSum(), 30, TOLERANCE);
    Assert.assertEquals(set2.getSumSquares(), 216, TOLERANCE);
    Assert.assertEquals(set2.getMean(), 5, TOLERANCE);
    stdev = set2.getStandardDeviation();
    Assert.assertEquals(stdev, 3.3166, TOLERANCE);
  }
  @Test
  public void testStrings() {

    VariableStatistics set1 = getVS1();
    String s = set1.toString();
    VariableStatistics set2 = new VariableStatistics(s);

    Assert.assertTrue(set1.equivalent(set2));
  }