i>ρ</mi></mtd><mtd columnalign="left" style="text-align: left; padding-left: 0"><mo>=</mo><mfrac><msubsup><mi>τ</mi><mi>w</mi><mn>2</mn></msubsup><mrow><msubsup><mi>τ</mi><mi>b</mi><mn>2</mn></msubsup><mo>+</mo><msubsup><mi>τ</mi><mi>w</mi><mn>2</mn></msubsup></mrow></mfrac><mo>,</mo></mtd></mtr></mtable><annotation encoding="application/x-tex">
\begin{aligned}
   \tau^2 &amp;= \tau_b^2 + \tau_w^2,\\
   \rho   &amp;= \frac{\tau_w^2}{\tau_b^2 + \tau_w^2},
\end{aligned}
</annotation></semantics></math> an