How to use jQuery to show/hide divs based on radio button selection?

Update 2015/06

As jQuery has evolved since the question was posted, the recommended approach now is using $.on

$(document).ready(function() {
    $("input[name=group2]").on( "change", function() {

         var test = $(this).val();
         $(".desc").hide();
         $("#"+test).show();
    } );
});

or outside $.ready()

$(document).on( "change", "input[name=group2]", function() { ... } );

Original answer

You should use .change() event handler:

$(document).ready(function(){ 
    $("input[name=group2]").change(function() {
        var test = $(this).val();
        $(".desc").hide();
        $("#"+test).show();
    }); 
});

should work