distribution.
 <p>
 For scale <code>k</code> and shape <code>α</code>, the variance is given by
 <ul>
 <li><code>∞</code> if <code>1 &lt; α &lt;= 2</code>,</li>
 <li><code>k^2 * α / ((α - 1)^2 * (α - 2))</code> otherwise.</li>
 </ul></div>
<dl><dt><span class="strong">Returns:</span></dt><dd>the variance (possibly <code>Double.POSITIVE_INFINITY</code> as
 for certain cases in <a href="../../../../../org/apache/commons/math3/distribution/TDistribution.html" title="class in org.apache.commons.math3.dis