 valign="top"><p>
            The random variable for the negative binomial distribution is the number
            of trials, (the number of successes is a fixed property of the distribution)
            whereas for the binomial, the random variable is the number of successes,
            for a fixed number of trials.
          </p></td></tr>
</table></div>
<p>
          It has the PDF:
        </p>
<p>
          <span class="inlinemediaobject"><img src="../../../../equations/neg_binomial_ref.svg"></span>
 