BasicStats { public static double variance(Path input, Path output, Configuration baseConf) throws IOException, InterruptedException, ClassNotFoundException { VarianceTotals varianceTotals = computeVarianceTotals(input, output, baseConf); return varianceTotals.computeVariance(); } private  BasicStats(); static double variance(Path input, Path output,
                                Configuration baseConf); static double varianceForGivenMean(Path input, Path output, double mean,
                                Configuration baseConf); static double stdDev(Path input, Path output,
                              Configuration baseConf); static double stdDevForGivenMean(Path input, Path output, double mean,
                              Configuration baseConf);  }
@Test public void testVar() throws Exception { Path input = getTestTempFilePath("stdDev/counts.file"); Path output = getTestTempFilePath("stdDev/output.file"); produceTestData(input); double v = BasicStats.variance(input, output, conf); assertEquals(2.44, v, 0.01); }