How to.. Get the avg of the checked row for the the values “value” checked in AngularJS + HTML

I'm learning AngularJS and now I want to know how to make the average of the checked values for the value entity, please teach/show me how.

Here you have a plunker w/ my code:

https://plnkr.co/edit/iBdEtQU1gPrCSxXQ2yyW?p=preview

And for those one who don't want to enter the link.

View HTML:

 <table style="border: 1px solid black">
  <thead>
  <tr>
    <th></th>
  <th>Id</th>
  <th>Name</th>
  <th>Address</th>
  <th>Value</th>
  </tr>
  <td><b>Total</b></td>
  <td></td>
  <td></td>
  <td></td>
  <td></td>
  </tr>
<tbody ng-repeat= "values in getSelected()">
    <td></td>
    <td></td>
    <td></td>
    <td></td>
    <td></td>
    </tbody>
    </thead>
</table>
</div>
<p>Average: </p>
  </body>

Controller code:

$scope.getSelected = function () {
  var ar = $scope.employees.filter(
    function (value) {
  if (value.checked == 1) {
    return true;
  } else {
    return false;
  }
}
);

  console.log(ar);
  return ar;
};
$scope.getSum = function() {
  return $scope.getSelected().reduce((sum, item) => {
return (sum + item.value);
  }, 0);
}
$scope.getAverage=function(){

}