ref.nmp.pdf">Probability Density
                    Function</a>
                  </p>
                </td>
<td>
                  <p>
                    The probability of obtaining <span class="bold"><strong>exactly k
                    failures</strong></span> from <span class="emphasis"><em>k</em></span> trials with success
                    fraction p. For example:
                  </p>
<pre class="programlisting"><span class="identifier">pdf</span><span class="special">(</span><span class="ide