code: public SampleSummaryStatistics combine(final SampleSummaryStatistics other) {
  		if (other._parameterCount != _parameterCount) {
  			throw new IllegalArgumentException(format(
  				"Expected sample size of %d, but got %d.",
  				_parameterCount, other._parameterCount
  			));
  		}
  
  		for (int i = 0; i < _parameterCount; ++i) {
  			_moments.get(i).combine(other._moments.get(i));
  			_quantiles.get(i).combine(other._quantiles.get(i));
  		}
  
  		return this;
  	}
docs: Combine two {@code SampleSummaryStatistics} statistic objects.
  
  @param other the other {@code SampleSummaryStatistics} statistics to
  combine with {@code this} one.
  @return {@code this} statistics object
  @throws IllegalArgumentException if the {@code parameterCount} of the
  {@code other} statistics object is different to {@code this} one
  @throws NullPointerException if the other statistical summary is
  {@code null}.