}
    if (count == 1) {
      return 0.0;
    }
    return ensureNonNegative(sumOfSquaresOfDeltas) / count;
  }

  /**
   * Returns the <a
   * href="http://en.wikipedia.org/wiki/Standard_deviation#Definition_of_population_values">
   * population standard deviation</a> of the values. The count must be non-zero.
   *
   * <p>This is guaranteed to return zero if the dataset contains only exactly one finite value. It

    }
    if (count == 1) {
      return 0.0;
    }
    return ensureNonNegative(sumOfSquaresOfDeltas) / count();
  }

  /**
   * Returns the <a
   * href="http://en.wikipedia.org/wiki/Standard_deviation#Definition_of_population_values">
   * population standard deviation</a> of the values. The count must be non-zero.
   *
   * <p>This is guaranteed to return zero if the dataset contains only exactly one finite value. It