RunningStats { public double variance() { if (numEntries == 0) { return 0; } return mean2 / numEntries; }  void push(double x); double mean(); double variance(); double stddev(); double skewness(); double kurtosis();  }
@Test public void testVariance() { RunningStats runningStats = new RunningStats(); runningStats.push(5); runningStats.push(6); runningStats.push(10); runningStats.push(14); runningStats.push(15); Assert.assertEquals(4.04969, runningStats.stddev(), 0.001); }