docs: private void addPreviewMeasurementSquaredDiffsToSum(
              List<double[]> meanMeasurements, 
              List<double[]> measurementsSquaredDiffSum, 
              Preview        preview, 
              int            numEntriesPerPreview)
      {
          List<double[]> previewMeasurements = preview.getData();
          
          // add standard deviation for each measurement in each entry
          for (int entryIdx = 0; entryIdx < numEntriesPerPreview; entryIdx++) {
              double[] meanEntry    = meanMeasurements.get(entryIdx);
              double[] previewEntry = previewMeasurements.get(entryIdx);
              double[] squaredDiffSumEntry;
              
              if (measurementsSquaredDiffSum.size() > entryIdx) {
                  squaredDiffSumEntry = measurementsSquaredDiffSum.get(entryIdx);
              }
              else {
                  // initialize sum entry
                  squaredDiffSumEntry = new double[previewEntry.length];
                  measurementsSquaredDiffSum.add(squaredDiffSumEntry);
              }
              
              // first measurement is used for indexing
              // -> simply copy from first preview
              if (squaredDiffSumEntry[0] == 0.0) {
                  squaredDiffSumEntry[0] = previewEntry[0];
              }
              
              // add squared differences for current entry
              for (int m = 1; m < previewEntry.length; m++) {
                  double diff        = (meanEntry[m] - previewEntry[m]);
                  double squaredDiff = diff * diff;
                  squaredDiffSumEntry[m] += squaredDiff;
              }
          }
      }