protected function unit_group($mform) {
        $grouparray = array();
        $grouparray[] = $mform->createElement('text', 'unit', get_string('unit', 'qtype_numerical'), array('size'=>10));
        $grouparray[] = $mform->createElement('float', 'multiplier',
                get_string('multiplier', 'qtype_numerical'), array('size'=>10));

        return $grouparray;
    }