sted in statistical applications should use the normalised
          (or <a href="http://mathworld.wolfram.com/RegularizedBetaFunction.html" target="_top">regularized</a>
          ) versions (ibeta and ibetac).
        </p>
<p>
          All of these functions require <span class="emphasis"><em>0 &lt;= x &lt;= 1</em></span>.
        </p>
<p>
          The normalized functions <a class="link" href="ibeta_function.html" title="Incomplete Beta Functions">ibeta</a>
          and <a class="link" href="ibeta_fun