code: public static <V> double getCohenD(final int baselineN, final double baselineMean, final double baselineStd, final int testN, final double testMean, final double testStd) {
          double pooledStd = Math.sqrt(((testN - 1) * Math.pow(testStd, 2) + (baselineN - 1) * Math.pow(baselineStd, 2)) / (baselineN + testN));
  
          double d = Math.abs(testMean - baselineMean) / pooledStd;
          return d;
      }
docs: Original Cohen's d formulation, as in Cohen (1988), Statistical power
  analysis for the behavioral sciences.
  
  @param <V> type of the keys of each map.
  @param baselineN number of samples of baseline method.
  @param baselineMean mean of baseline method.
  @param baselineStd standard deviation of baseline method.
  @param testN number of samples of test method.
  @param testMean mean of test method.
  @param testStd standard deviation of test method.
  @return Cohen's d without least squares estimation.