@Test
public void testGetDelta() {

	assertEquals(Double.NaN, list1.getDelta());
	list1.addValue(-1L, 10F);
	list1.addValue(-2L, -3F);
	list1.addValue(30L, 3F);
	list1.addValue(2L, -100F);
	list1.addValue(31L, -102F);
	/* expected = sqrt((10+89/3)^2+(3+89/3)^2+(-102+89/3)^2)/3 */
	assertEquals(29.03, list1.getDelta());
}