Independent Samples T-Test - Comparing Two Proportions

Where $g_1$ and $g_2$ are the two proportions and $n_1$ and $n_2$ are the sample sizes:

$z=\frac{g_1-g_2}{\sqrt{g_{12}(1-g_{12})(n^{-1}_1+n^{-1}_2)}}$

where:

$g_{12}=\frac{n_1 g_1 + n_2 g_2}{n_1+n_2}$

where $p \approx 2 \Pr(t_{n_1+n_2-2} \ge |t|)$.