# How To Calculate Standard Deviation in JavaScript

By onjsdev

Dec 23rd, 2023

Standard deviation is a measure of how spread out a set of data is from its mean. In this article we will show you how to calculate standard deviation of a array of numbers with Javascript.

Let's get started.

## How To Calculate Standard Deviation With Javascript

Before implementing the code, let's examine the formula of standard deviation of an array of numbers.

Formula: `SD = √(Σ(x - μ)^2 / n)`

Where:

- x is a data in array,
- μ is the mean,
- n is the length of the array,
- Σ is the sum of

To implement the formula, we will use an array of numbers and the following JavaScript array methods to calculate the different portions of the formula:

`Math.sqrt`

=> Square Root`Math.pow`

=> Square`map`

=> (x - μ)^2`reduce`

=> calculating mean and Σ((x - μ)^2)

And here is implementation calculating the standard deviation of an array.

```
// A Dataset
const numbers = [2, 6, 7];
// Calculate mean
const mean = numbers.reduce((acc, curr) => acc + curr) / numbers.length;
// For the sample numbers.length - 1
const length = numbers.length;
const sd = Math.sqrt(
numbers
.map((number) => Math.pow(number - mean, 2))
.reduce((acc, curr) => acc + curr) / length
);
console.log(sd);
// 2.1602
```

## Conclusion

To sum up, standart deviation is usefeul measure that indicate variability in a dataset. In this article, we have shown how to calculate the standard deviation of an array of numbers in javascript.

Thank you for reading.