sum(questioncode_1.NAOK == 'Y', questionscode_2.NAOK == 'Y', ....

{list(questioncode.shown)} 

Which car(s) do you own? <script type="text/javascript" charset="utf-8">
 
        $(document).ready(function() {
                //// Identify the hidden question input
                //// EDIT HERE (1) - replace with your hidden question input ID
                var hiddenInput = 'answer​#119459X725X11680';
 
                //// Identify the checkboxes to be randomized
                //// EDIT HERE (3) - add or remove as required, 
                //// replace with your checkbox IDs
                var CB1 = '#answer119459X725X11664A';
                var CB2 = '#answer119459X725X11664B';
                var CB3 = '#answer119459X725X11664C';
 
                //// Create an array of all checkboxes to be randomized
                //// EDIT HERE (4) - add or remove CBs as required
                checkBoxes = new Array( CB1, CB2, CB3 );
                var checkBoxesLength = checkBoxes.length;
 
                //// The randomizing function - no editing required
                function randomResponse () {
                        var boxLabels = new Array();
 
                        // loop through all of the checkboxes and if they are checked, 
                        // add their label to the boxLabels array
                        for( var i=0; i<checkBoxesLength; i++ ) {
                                if ( $(checkBoxes[i]).attr('checked') == true ) {
                                        var cbid = checkBoxes[i].replace('#','');
                                        boxLabels.push( $( 'label[for=' + cbid + ']' ).html() );
                                }
                        }
 
                        // find a random index of the responses array
                        var randomNum = Math.floor(Math.random() * boxLabels.length); 
 
                        // populate the hidden question input with the 
                        // random input value
                        $(hiddenInput).val( boxLabels[randomNum] ); 
                }
 
                //// The listeners that will fire the randomize function if a 
                //// change occurs in the checkboxes
                //// EDIT HERE (5) - add or remove CBs as required
                $(CB1).change(function() {
                        randomResponse ();
                });
                $(CB2).change(function() {
                        randomResponse ();
                });
                $(CB3).change(function() {
                        randomResponse ();
                });
 
        });
</script>