code: function sample_skewness(x) {
          // The skewness of less than three arguments is null
          if (x.length < 3) return null;
  
          var n = x.length,
              cubed_s = Math.pow(sample_standard_deviation(x), 3),
              sum_cubed_deviations = sum_nth_power_deviations(x, 3);
  
          return n * sum_cubed_deviations / ((n - 1) * (n - 2) * cubed_s);
      }
docs: # [Skewness](http://en.wikipedia.org/wiki/Skewness)  A measure of the extent to which a probability distribution of a real-valued random variable "leans" to one side of the mean. The skewness value can be positive or negative, or even undefined.  Implementation is based on the adjusted Fisher-Pearson standardized moment coefficient, which is the version found in Excel and several statistical packages including Minitab, SAS and SPSS.  Depends on `sum_nth_power_deviations()` and `sample_standard_deviation`