.js

$scope.submit = function() {

        if($scope.question_type_id==1){ // if no answer(s) are selected - error!
            if(!$scope.selectedItem){
                alertService.add('danger', 'Please select at least one answer', 5000);
                return false;
            }
        }
        
        if($scope.question_type_id==2){ // if no answer(s) are selected - error!
            if(!$scope.slider.value){
                alertService.add('danger', 'Please select at least one answer', 5000);
                return false;
            }
        }
        
}