jquery validation plugin help

This code is working fine


<script>


$.validator.setDefaults({



submitHandler: function() {


$('#signup_form').ajaxForm();


var options = {
target: '#result', // target element(s) to be updated with server response
beforeSubmit: showRequest, // pre-submit callback
success: showResponse, // post-submit callback
clearForm: true, // clear all form fields after successful submit
resetForm: true // reset the form after successful submit
};




$('#signup_form').Submit(options);







}
});


but when i use this code , my form is submiited even its not validated



<script>


$.validator.setDefaults({



submitHandler: function() {


$('#signup_form').ajaxForm();


var options = {
target: '#result', // target element(s) to be updated with server response
beforeSubmit: showRequest, // pre-submit callback
success: showResponse, // post-submit callback
clearForm: true, // clear all form fields after successful submit
resetForm: true // reset the form after successful submit
};




$('#signup_form').submit(function(){



$(this).ajaxSubmit(options);


});






}
});