  <p>
                    and
                  </p>
                  <p>
                    p = <a class="link" href="../../sf_beta/ibeta_function.html" title="Incomplete Beta Functions">ibeta</a>(v2
                    / 2, v1 / 2, v2 / (v2 + v1 * x))
                  </p>
                  <p>
                    The first is used for v1 * x &lt; v2, otherwise the second is
                    used.
                  </p>
                  <p>
                    The aim is to keep the <span class="em