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 d e f f × g 12 ( 1 − g 12 ) ( n 1 − 1 + n 2 − 1 ) {\displaystyle z={\frac {g_{1}-g_{2}}{\sqrt {d_{eff}\times g_{12}(1-g_{12})(n_{1}^{-1}+n_{2}^{-1})}}}}
where: