Change text in post excerpt metabox

Change Excerpt Text

/**
 * Change the Excerpt text and description
 */
function change_excerpt_name( $translated_text, $text, $domain ) {
    if ( $_GET['post_type'] == 'staff' ) {
        switch ( $translated_text ) {
            case 'Excerpt' :
                $translated_text = 'Staff Role/Position';
                break;
            case 'Excerpts are optional hand-crafted summaries of your content that can be used in your theme. <a href="http://codex.wordpress.org/Excerpt" target="_blank">Learn more about manual excerpts.</a>' :
                $translated_text = 'This is the role of the Church Staff Member. Use sentence case e.g. Communication Director';
                break;
        }
    }
    return $translated_text;
}
add_filter( 'gettext', 'change_excerpt_name', 20, 3 );