Could someone tell me why this is not working?

```
<!DOCTYPE html>
<html>
<head>
<script>
window.onload = initPage;

function initPage() {
    document.getElementById("member_type_academic_4").onChange=alert("It's Working");
}
</script>
</head>
<body>

<form>
  <label for="member_type_academic_4">test</label>
  <select name="member_type_academic_4" id="member_type_academic_4">
    <option value="0" selected>Select One</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
  </select>
</form>

</body>
</html>

```

It will fire the alert box when the window loads, but not when there is a change on the select box. I know it's something simple that I'm missing. Thanks!