const stats = {
  max: 56.78,
  standard_deviation: 4.34,
  median: 34.54,
  mode: 23.87,
  min: -0.75,
  average: 35.85
};
const half = (function() {

  return function half(stats) {
    return (stats.max + stats.min) / 2.0;
  };

})();
console.log(stats); 
console.log(half(stats));