docs: public double getSampleSkewness() {
      if(!(m2 > 0) || !(n > 2)) {
        throw new ArithmeticException("Skewness not defined when variance is 0 or weight <= 2.0!");
      }
      return (m3 * n / (n - 1) / (n - 2)) / FastMath.pow(getSampleVariance(), 1.5);
    }