Where g 1 {\displaystyle g_{1}} and g 2 {\displaystyle g_{2}} are the two proportions and n 1 {\displaystyle n_{1}} and n 2 {\displaystyle n_{2}} are the sample sizes:
z = g 1 − g 2 g 12 ( 1 − g 12 ) ( n 1 − 1 + n 2 − 1 ) {\displaystyle z={\frac {g_{1}-g_{2}}{\sqrt {g_{12}(1-g_{12})(n_{1}^{-1}+n_{2}^{-1})}}}}
where:
where p ≈ 2 Pr ( t n 1 + n 2 − 2 ≥ | t | ) {\displaystyle p\approx 2\Pr(t_{n_{1}+n_{2}-2}\geq |t|)} .
