Where \(\bar{x} \) is the observed mean, \(e\) is the expected value, \(s\) is the sample standard deviation and \(n\) is the effective sample size,
\[\begin{align} t = \sqrt{nd_{eff}}\frac{\bar x - e}{s}\end{align}\]
where \(t = \sqrt{nd_{eff}}\frac{\bar x - e}{s}\) if \(\bar x \ne e\) and NaN otherwise, and \(d_{eff}\) is Extra deff (see Weights, Effective Sample Size and Design Effects).
Note that if you wish to replicate results from IBM SPSS Data Collection products (including Survey Reporter and Quantum) additional settings need to be modified (see How to Replicate Survey Reporter Significance Tests).