# Learn Advanced Array Methods by Building a Statistics Calculator - Step 48

### Tell us what’s happening:

I’m confused on which initial value to set to 0. Should it be in the sumSquaredDifferences variable or should it be in the callback function?

``````<!-- file: index.html -->

``````
``````/* file: styles.css */

``````
``````/* file: script.js */
// User Editable Region

const getVariance = (array) => {
const mean = getMean(array);
const differences = array.map(
el => el - mean
);
const squaredDifferences = differences.map(
el => el ** 2
);
const sumSquaredDifferences = squaredDifferences.reduce((acc, el) => acc + el);
}

// User Editable Region
``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36`

### Challenge Information:

Learn Advanced Array Methods by Building a Statistics Calculator - Step 48

Hi @KoduFCC

Remember to set the initial value to `0` .

I know about the initial value, but I’m not sure about the position.

Check your previous code which uses the `.reduce()` method.

I figured it out finally. I just didn’t think right.