title: .attr('checked','checked') does not work
body: <p>I am trying to check radio. Neither the following works:</p>
  
  <p>[edit]</p>
  
  <pre><code>$('selector').attr('checked','checked');
  $('selector').attr('checked',true);
  </code></pre>
  
  <p>The two alert() in the following code show "1" and "a", respectively. My expectation is the second alert() showing "b".</p>
  
  <p>Opera does check the second radio box in its browser, but its element inspector, dragonfly, shows that the DOM is not changed.</p>
  
  <p>[end edit]</p>
  
  <p>I had read the FAQ before I posted this question:</p>
  
  <p><a href="http://docs.jquery.com/Frequently_Asked_Questions#How_do_I_check.2Funcheck_a_checkbox_input_or_radio_button.3F">http://docs.jquery.com/Frequently_Asked_Questions#How_do_I_check.2Funcheck_a_checkbox_input_or_radio_button.3F</a></p>
  
  <p>Helps will be much appreciated!</p>
  
  <p>TIA</p>
  
  <p>The xhtml page and code follows:</p>
  
  <pre><code>&lt;!DOCTYPE html 
       PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
       "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt;
  &lt;head&gt;
  &lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8"/&gt;
  &lt;title&gt;Weird Behavior&lt;/title&gt;
  &lt;script type="text/javascript" src="scripts/jquery.js"/&gt;
  &lt;script type="text/javascript"&gt;
  function clickme(){
      alert($('input[name="myname"][value="b"]').length);
      $('input[name="myname"][value="b"]').attr('checked','checked');
      $('#b').attr('checked',true);
      alert($('input[name="myname"][checked]').val());
  };
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form action=""&gt;
          &lt;fieldset&gt;
              &lt;legend&gt;Why check is not switched?&lt;/legend&gt;
              &lt;input type="radio" name="myname" value="a" id="a" checked="checked"/&gt;A
              &lt;input type="radio" name="myname" value="b" id="b"/&gt;B
          &lt;/fieldset&gt;
      &lt;/form&gt;
      &lt;p&gt;
      &lt;button type="button" onclick="clickme()"&gt;click me&lt;/button&gt;
      &lt;/p&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>