Variance is a tool used in statistics to measure how spread out the numbers are in a group. It helps to show how different each number is from the average (or mean) of the group.

In this article we will show you how to calculate variance with javascript for a given array consisting of numbers. Let's get started.

## CALCULATE VARIANCE WITH JAVASCRIPT

You can see the formula below for calculating the variance of a dataset.

Formula: **V = (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

In the following example, we will utilize an array containing numbers, and the following JavaScript array methods will be applied to compute various portions of the formula.

**Math.pow**=> Square**map**=> (x - μ)^2**reduce**=> calculating mean and Σ((x - μ)^2)

A Note: Sample vs Population In Variance

When we want to calculate the variance for a sample that is taken for entire data(population), the formula will undergo a minor modification, as follows:

Formula: **V = (Σ(x - μ)^2 / (n-1))**

And here is a code snippet calculating the variance of an array.

```
// A Dataset
const numbers = [1, 2, 3, 4, 5];
// Calculate mean
const mean = numbers.reduce((acc, curr) => acc + curr) / numbers.length;
// For the sample numbers.length - 1
const length = numbers.length;
const v =
numbers
.map((number) => Math.pow(number - mean, 2))
.reduce((acc, curr) => acc + curr) / length;
console.log(v); // 2
```

## Conclusion

In conclusion, variance is usefeul measure that indicate variability in a data set and we have shown how to calculate it with javascript using array methods and math library.

Thank you for reading.