How to undo a radio button selection using JavaScript or preferably jQuery

Question

I am working in a scenario with a group of radio button selections. The requirement is that only 2 can be selected Yes. So, if the third is also selected "Yes", I want to revert it to "No"

Additionally I would also like to know if I can just check if a given index of Radio button within a group is checked instead of doing this: "($(this).is(':checked') && $(this).val() == 'Y')"

jsFiddle Link: http://jsfiddle.net/pshah331/S8qep/

HTML:

<p>Folder A:
    <input type="radio" name="folder_A" value="Y" onclick="folderSelectionChanged()" />Yes
    <input type="radio" name="folder_A" value="N" onclick="folderSelectionChanged()" />No</p>
<p>Folder B:
    <input type="radio" name="folder_B" value="Y" onclick="folderSelectionChanged()" />Yes
    <input type="radio" name="folder_B" value="N" onclick="folderSelectionChanged()" />No</p>
<p>Folder C:
    <input type="radio" name="folder_C" value="Y" onclick="folderSelectionChanged()" />Yes
    <input type="radio" name="folder_C" value="N" onclick="folderSelectionChanged()" />No</p>
<div id="update"></div>

JavaScript in "HEAD":

function folderSelectedYesCount() {
    var yesCount = 0;
    var folderRadioGroups = $("input[name^='folder_']");


    folderRadioGroups.each(function () {
        // TODO:  Would like to check by index --> "index 0 is selected/checked"
        if ($(this).is(':checked') && $(this).val() == 'Y') {
            yesCount++;
        }
    });

    return yesCount;
}

function folderSelectionChanged() {
    // TODO:  If count of Yes is greater than 2, then change the last clicked to "No"
    /*
    if (folderSelectedYesCount() > 1){
        $(this)[1].prop('checked', true);
    }
    */

    $('#update').html('Selection count for "Yes" is <b>' + folderSelectedYesCount() + ' </b>');
}

Answer 1

Changed html so folderSelectionChanged function can take this as argument to handle the events like this:

if(folderSelectedYesCount() > 2){
    $(obj).prop('checked', false);
    $(obj).next().prop('checked', true);
}

fiddle

Answer 2

I have updated your jsfiddle please check :-

function folderSelectionChanged(e) {

    if(folderSelectedYesCount()>2){
        $(e).siblings().prop("checked",true);         
    }
    $('#update').html('Selection count for "Yes" is <b>' + folderSelectedYesCount() + ' </b>');
}

click here :- http://jsfiddle.net/S8qep/47/

Thanks