Edit in JSFiddle

changeRadioValues();

$("input[name=radio_agree]").change(function(){
	changeRadioValues();
});

function changeRadioValues(){
  var radio_value1 = $("input[name=radio_agree]:checked").val();
  var radio_value2 = $(':radio[name=radio_agree]:checked').val();
  var radio_value3 = $("input:radio[name=radio_agree]:checked").val();

  $("#result1").html(radio_value1);
  $("#result2").html(radio_value2);
  $("#result3").html(radio_value3);
}

function agreeYes(){
	$("#radio_agree_yes").prop("checked", true).change();
  //$('input[name=radio_agree][value=Y]').prop("checked", true).change();
}

function agreeNo(){
	//$("#radio_agree_no").prop("checked", true).change();
  $('input[name=radio_agree][value=N]').prop("checked", true).change();
}

function uncheckRadio(){
	$('input:radio[name="radio_agree"]:checked').prop("checked", false);
}

function isCheckedRadio(){
	var result = $("input[name=radio_agree]").is(":checked");
	$("#result_text").html('$("input[name=radio_agree]").is(":checked") = ' + result);
}

function getCheckedRadioValue(){
  var result = $("input[name=radio_agree]:checked").val();
  $("#result_text").html('$("input[name=radio_agree]:checked").val() = ' + result);    
}