code: function onData( data, encoding, clbk ) {
  		var numData = data.length,
  			sum = 0;
  
  		for ( var i = 0; i < numData; i++ ) {
  			sum += data[ i ];
  		}
  		clbk( null, sum/numData );
  	}
docs: FUNCTIONS // 
  FUNCTION: onData( data, encoding, clbk )
  Data event handler. Calculates the mean.
  
  @private
  @param {Array} data - streamed data array
  @param {String} encoding
  @param {Function} clbk - callback to invoke after handling streamed data. Function accepts two arguments: [ error, chunk ].