Radio button click event

Hi,

I am trying to make an event after clicking on the choice radio button. My code is so simple and it works fine in a test html page put within the SSI web pages it is not working.

I put the following code on the Survey Settings --> Header and Footers --> Footer section

<script>
$("input[type='radio']").click(function() {
alert("click");
});
</script>

I think it is so simple but I did'nt get it as I am still new to this software.
Thanks in advance