Trying to fill text box with dropdown value but the text box value is remaining blank

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script type="text/javascript" src="/path/to/jquery.plug-in.js"></script>

<div>
    <select id="sb1" class="ddl">
        <option title="1"> 1</option>
        <option title="2"> 2</option>
        <option title="3"> 3</option>
    </select>

    <input id="myText" class="text" />
</div>

<script type="text/javascript">
    $(document).ready(function () {
            $("#<%= ddlName.ClientID %>").change(function () {
                 $("#<%= tbName.ClientID %>") = this.value;
            });

            $("#<%= ddlState.ClientID %>").change(function () {
                 $("#<%=tbState.ClientID %>") = this.value;
            });
        });
 </script>