### Question:
ClusterSampling { public static double xbarStd(TransposeDataCollection sampleDataCollection, int populationM, double Nbar) { return Math.sqrt(xbarVariance(sampleDataCollection, populationM, Nbar)); }  static double nBar(TransposeDataList clusterIdList); static TransposeDataCollection randomSampling(TransposeDataList clusterIdList, int sampleM); static double mean(TransposeDataCollection sampleDataCollection); static double xbarVariance(TransposeDataCollection sampleDataCollection, int populationM, double Nbar); static double xbarStd(TransposeDataCollection sampleDataCollection, int populationM, double Nbar);  }### Answer:
@Test public void testXbarStd() { logger.info("xbarStd"); TransposeDataCollection sampleDataCollection = generateSampleDataCollection(); int populationM = 4; double Nbar = 10.0; double expResult = 1.4142135623731; double result = ClusterSampling.xbarStd(sampleDataCollection, populationM, Nbar); assertEquals(expResult, result, Constants.DOUBLE_ACCURACY_HIGH); }