code: function skewness( arr ) {
  	if ( !Array.isArray( arr ) ) {
  		throw new TypeError( 'skewness()::invalid input argument. Must provide an array.' );
  	}
  	var len = arr.length,
  		delta = 0,
  		delta_n = 0,
  		term1 = 0,
  		N = 0,
  		mean = 0,
  		M2 = 0,
  		M3 = 0,
  		g;
  
  	for ( var i = 0; i < len; i++ ) {
  		N += 1;
  
  		delta = arr[ i ] - mean;
  		delta_n = delta / N;
  
  		term1 = delta * delta_n * (N-1);
  
  		M3 += term1*delta_n*(N-2) - 3*delta_n*M2;
  		M2 += term1;
  		mean += delta_n;
  	}
  	// Calculate the population skewness:
  	g = Math.sqrt( N )*M3 / Math.pow( M2, 3/2 );
  
  	// Return the corrected sample skewness:
  	return Math.sqrt( N*(N-1))*g / (N-2);
  }
docs: FUNCTION: skewness( arr )
  Computes the sample skewness of an array of values.
  
  @param {Array} arr - array of values
  @returns {Number} sample skewness