You could just use the bound ng-model
(answers[item.questID]
) value itself in your ng-change method to detect if it has been checked or not.
Example:-
<input type="checkbox" ng-model="answers[item.questID]"
ng-change="stateChanged(item.questID)" /> <!-- Pass the specific id -->
and
$scope.stateChanged = function (qId) {
if($scope.answers[qId]){ //If it is checked
alert('test');
}
}