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

This function works and produces the same result as numjs

const st = (numbers) => {
  const mean = numbers.reduce((acc, item) => acc + item) / numbers.length;
  return Math.sqrt(numbers.reduce((acc, item) => acc + Math.pow((parseFloat(item) -mean), 2)))
}