Standard deviation javascript

Question

I am trying to get the standard deviation of a user input string. I have as follows, but it returns the wrong value for SD. The calculation should go as follows: Sum values/

Answer 1

function StandardDeviation(numbersArr) {
    //--CALCULATE AVAREGE--
    var total = 0;
    for(var key in numbersArr) 
       total += numbersArr[key];
    var meanVal = total / numbersArr.length;
    //--CALCULATE AVAREGE--
  
    //--CALCULATE STANDARD DEVIATION--
    var SDprep = 0;
    for(var key in numbersArr) 
       SDprep += Math.pow((parseFloat(numbersArr[key]) - meanVal),2);
    var SDresult = Math.sqrt(SDprep/numbersArr.length);
    //--CALCULATE STANDARD DEVIATION--
    alert(SDresult);
    
}

var numbersArr = [10, 11, 12, 13, 14];
StandardDeviation(numbersArr);