Standard Deviation

standard-deviation.js

function standardDeviation (values) {
  
  var avg = average(values);
  
  var squareDiffs = values.map(function (value) {
    
    var diff = value - avg,
        sqrDiff = diff * diff;
    
    return sqrDiff;
  });
  
  var avgSquareDiff = average(squareDiffs);
 
  var stdDev = Math.sqrt(avgSquareDiff);
  
  return stdDev;
}
 
function average (data) {
  
  var sum = data.reduce(function (sum, value) {
    
    return sum + value;
  }, 0);
 
  var avg = sum / data.length;
  
  return avg;
}

var stdDev = standardDeviation([1, 2, 3, 4, 5, 6, 7, 8, 9, 25]);