\begin{align*}
\tau_{\text{Wald}} = \frac{n}{\hat{\sigma}^2}(\hat{\theta}-\hat{\theta}^{\text{(Null)}})^T\left\{\frac{1}{n}\sum_{j=1}^nf(X^{\dagger}_j)f(X^{\dagger}_j)^T\right\}(\hat{\theta}-\hat{\theta}^\text{(Null)}),
\end{align*}
