>Use this method to get the numerical value of the mean of this
 distribution.

 For shape parameter <code>alpha</code> and scale parameter <code>beta</code>, the
 mean is <code>alpha * beta</code>.</div>
<dl><dt><span class="strong">Returns:</span></dt><dd>the mean or <code>Double.NaN</code> if it is not defined</dd></dl>
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<h4>getNumericalVariance</h4>
<pre>public&nbsp;double&nbsp;getNumericalVariance