*/
  @Override
  public boolean equals(@Nullable Object obj) {
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    PairedStats other = (PairedStats) obj;
    return xStats.equals(other.xStats)
        && yStats.equals(other.yStats)
        && doubleToLongBits(sumOfProductsOfDeltas) == doubleToLongBits(other.sumOfProductsOfDeltas);
  }

  /**