For a hypothesis test of the form $\begin{align} H_0 : \theta = \theta_0 && H_1 : \theta \ne \theta_0 \end{align} $ the general form of the test statistic is $s(x) = \frac{\hat \theta - \theta_0}{\hat {s.e.}(\hat \theta)}$ Typically we want to find a test statistic for which we know the distribution.