code: public static Collector<Sample, ?, SampleSummaryStatistics>
  	toSampleStatistics(final int parameterCount) {
  		require.positive(parameterCount);
  
  		return Collector.of(
  			() -> new SampleSummaryStatistics(parameterCount),
  			SampleSummaryStatistics::accept,
  			SampleSummaryStatistics::combine
  		);
  	}
docs: Return a {@code Collector} which applies an double-producing mapping
  function to each input element, and returns moments-statistics for the
  resulting values.
  
  <pre>{@code
  final Stream<Sample> stream = ...
  final SampleSummaryStatistics statistics = stream
  .collect(toDoubleMomentStatistics(parameterCount));
  }</pre>
  
  @param parameterCount the number of parameter of the accumulated
  {@code Sample} objects
  @return a {@code Collector} implementing the sample reduction
  @throws IllegalArgumentException if the given {@code parameterCount}
  is smaller then one