Angularjs set rootScope with input radio ngModel

Question

Who knows why it doesn't works ?

i want to set a $rootScope value with ngModel on my radio button.

that's an example jsFiddle

    <form  name="pageTwoForm">
        <h3>General Information > Knowledge About </h3>
        <div>
        <b>User</b>
            <div ng-repeat="option in userOptions">
                <input type="radio" ng-model="knowledgeAboutUser" ng-value="option.id" />{{option.text}}
            </div>

<b>Target Group</b>
            <div ng-repeat="option in targetGroupUserOptions">
                <input type="radio" ng-model="$parent.knowledgeAboutTargetGroup" ng-value="option.id" />
                {{option.text}}
            </div>
    </div>
</form>
    <h3 >{{knowledgeAboutTargetGroup}}</h3>
    <h3 >{{knowledgeAboutUser}}</h3> 

Answer 1

i solved it

    <form  name="pageTwoForm">
        <h3>General Information > Knowledge About </h3>
        <div>
        <b>User</b>
            <div ng-repeat="option in userOptions">
                <input type="radio" ng-model="data.knowledgeAboutUser" ng-value="option.id" />{{option.text}}
            </div>

<b>Target Group</b>
            <div ng-repeat="option in targetGroupUserOptions">
                <input type="radio" ng-model="data.knowledgeAboutTargetGroup" ng-value="option.id" />
                {{option.text}}
            </div>
    </div>
</form>
    <h3 >{{data.knowledgeAboutTargetGroup}}</h3>
    <h3 >{{data.knowledgeAboutUser}}</h3> 

i don't know why but it works if i use

data.knowledgeAboutUser

not only

knowledgeAboutUser