 class="desc" /></colgroup>
    <tr>
      <th>pre_test</th>
      <td><p>Required. data.frame carrying responses to pre-test questions.</p></td>
    </tr>
    <tr>
      <th>pst_test</th>
      <td><p>Required. data.frame carrying responses to post-test questions.</p></td>
    </tr>
    <tr>
      <th>subgroup</th>
      <td><p>a Boolean vector identifying the subset. Default is NULL.</p></td>
    </tr>
    <tr>
      <th>force9</th>
      <td><p>Optional. There are cases where DK data doesn't have DK. But