</p>
 <p>
 <code>SSE = SYY - (SXY * SXY / SXX)</code></p>
 <p>
 where <code>SYY</code> is the sum of the squared deviations of the y
 values about their mean, <code>SXX</code> is similarly defined and
 <code>SXY</code> is the sum of the products of x and y mean deviations.
 </p><p>
 The sums are accumulated using the updating algorithm referenced in
 <a href="../../../../../../org/apache/commons/math3/stat/regression/SimpleRegression.html#addData(double, double)"><code>addData(double, double)</code></a>.</p