@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class PairedStatsAccumulator {

  // These fields must satisfy the requirements of PairedStats' constructor as well as those of the
  // stat methods of this class.
  private final StatsAccumulator xStats = new StatsAccumulator();
  private final StatsAccumulator yStats = new StatsAccumulator();
  private double sumOfProductsOfDeltas = 0.0;