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The final step in calculating the variance is to divide the sum of the squared differences by the count of numbers.

Divide your .reduce() call by the length of the array (in your variance declaration). Then, return variance.

--hints--

You should divide the result of the .reduce() call by the length of the array.

assert.match(getVariance.toString(), /variance\s*=\s*array\.reduce\(\s*function\s*\(\s*acc\s*,\s*el\s*\)\s*\{\s*var\s+difference\s*=\s*el\s*-\s*mean\s*;\s*var\s+squared\s*=\s*Math\.pow\(\s*difference\s*,\s*2\s*\)\s*;?\s*return\s+acc\s*\+\s*squared\s*;\s*\}\s*,\s*0\s*\)\s*\/\s*array\.length\s*;?/);

You should return the value of variance.

assert.match(getVariance.toString(), /return\s+variance\s*;/);

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html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="./styles.css" />
    <script src="./script.js"></script>
    <title>Statistics Calculator</title>
  </head>
  <body>
    <h1>Statistics Calculator</h1>
    <p>Enter a list of comma-separated numbers.</p>
    <form onsubmit="calculate(); return false;">
      <label for="numbers">Numbers:</label>
      <input type="text" name="numbers" id="numbers" />
      <button type="submit">Calculate</button>
    </form>
    <div class="results">
      <p>
        The <dfn>mean</dfn> of a list of numbers is the average, calculated by
        taking the sum of all numbers and dividing that by the count of numbers.
      </p>
      <p class="bold">Mean: <span id="mean"></span></p>
      <p>
        The <dfn>median</dfn> of a list of numbers is the number that appears in
        the middle of the list, when sorted from least to greatest.
      </p>
      <p class="bold">Median: <span id="median"></span></p>
      <p>
        The <dfn>mode</dfn> of a list of numbers is the number that appears most
        often in the list.
      </p>
      <p class="bold">Mode: <span id="mode"></span></p>
      <p>
        The <dfn>range</dfn> of a list of numbers is the difference between the
        largest and smallest numbers in the list.
      </p>
      <p class="bold">Range: <span id="range"></span></p>
      <p>
        The <dfn>variance</dfn> of a list of numbers measures how far the values
        are from the mean, on average.
      </p>
      <p class="bold">Variance: <span id="variance"></span></p>
      <p>
        The <dfn>standard deviation</dfn> of a list of numbers is the square
        root of the variance.
      </p>
      <p class="bold">
        Standard Deviation: <span id="standardDeviation"></span>
      </p>
    </div>
  </body>
</html>

css

body {
  margin: 0;
  background-color: rgb(27, 27, 50);
  text-align: center;
  color: #fff;
}

button {
  cursor: pointer;
  background-color: rgb(59, 59, 79);
  border: 3px solid white;
  color: white;
}

input {
  background-color: rgb(10, 10, 35);
  color: white;
  border: 1px solid rgb(59, 59, 79);
}

.bold {
  font-weight: bold;
}

const getMean = (array) => array.reduce((acc, el) => acc + el, 0) / array.length;

const getMedian = (array) => {
  const sorted = array.toSorted((a, b) => a - b);
  const median =
    sorted.length % 2 === 0
      ? getMean([sorted[sorted.length / 2], sorted[sorted.length / 2 - 1]])
      : sorted[Math.floor(sorted.length / 2)];
  return median;
}

const getMode = (array) => {
  const counts = {};
  array.forEach(el => counts[el] = counts[el] ? counts[el] + 1 : 1);

  if (new Set(Object.values(counts)).size === 1) {
    return null;
  }
  const highest = Object.keys(counts).sort(
    (a, b) => counts[b] - counts[a]
  )[0];
  const mode = Object.keys(counts).filter(
    (el) => counts[el] === counts[highest]
  );
  return mode.join(", ");
}

const getRange = (array) => {
  return Math.max(...array) - Math.min(...array);
}

--fcc-editable-region--
const getVariance = (array) => {
  const mean = getMean(array);
  const variance = array.reduce((acc, el) => {
    const difference = el - mean;
    const squared = difference ** 2;
    return acc + squared;
  }, 0);
}
--fcc-editable-region--

const calculate = () => {
  const value = document.querySelector("#numbers").value;
  const array = value.split(/,\s*/g);
  const numbers = array.map(el => Number(el)).filter(el => !isNaN(el));

  const mean = getMean(numbers);
  const median = getMedian(numbers);
  const mode = getMode(numbers);
  const range = getRange(numbers);

  document.querySelector("#mean").textContent = mean;
  document.querySelector("#median").textContent = median;
  document.querySelector("#mode").textContent = mode;
  document.querySelector("#range").textContent = range;
}

Step 53

--description--

--hints--

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