r bound
          on the success fraction, whilst many texts refer to this method as giving
          an "exact" result in practice it produces an interval that guarantees
          <span class="emphasis"><em>at least</em></span> the coverage required, and may produce pessimistic
          estimates for some combinations of <span class="emphasis"><em>failures</em></span> and <span class="emphasis"><em>successes</em></span>.
          See:
        </p>
<p>
          <a href="http://www.ucs.louisiana.edu/~kxk