code: package org.omnetpp.scave.writers;
  
  /**
   * Extends IStatisticalSummary with weighted statistics.
   *
   * @author Andras
   */
  public interface IStatisticalSummary2 extends IStatisticalSummary {
  
      /**
       * Returns whether this is weighted statistics.
       */
      boolean isWeighted();
  
      /**
       * Returns the sum of weights.
       * @return The value or Double.NaN if no values have been added
       */
      double getWeights();
  
      /**
       * Returns the sum of weight*value products.
       * @return The value or Double.NaN if no values have been added
       */
      double getWeightedSum();
  
      /**
       * Returns the sum of squared weights.
       * @return The value or Double.NaN if no values have been added
       */
      double getSqrSumWeights();
  
      /**
       * Returns the sum of weight*value*value products.
       * @return The value or Double.NaN if no values have been added
       */
      double getWeightedSqrSum();
  }
  