   - parameter values: Array of decimal numbers.
   - returns: The median value from the array. Returns nil for an empty array. Returns the greater of the two middle values if there is an even number of items in the array.
 
-  Example
+  Example:
 
       Sigma.medianHigh([1, 12, 19.5, 10, 3, -5]) // 10
    

  - parameter values: Array of decimal numbers.
  - returns: Variance based on a sample. Returns nil when the array is empty or contains a single value.
  
  Formula
  
      s^2 = Σ( (x - m)^2 ) / (n - 1)
  


  n is the sample size.

  Example:

      Sigma.standardDeviationSample([1, 12, 19.5, -5, 3, 8]) // 8.674195447801869

