ni={p(1p)+p(1p)}(ZE)2={0.12(10.12)+0.12(10.12)}(1.960.04)2=507.1

Description:

Math equation. Using the previous equation for sample sizes for two independent samples with a dichotomous outcome, the samples sizes in this example will be computed by taking the quantity 0.12 times (1-0.12) plus 0.12 times (1-0.12) and multiplying this times the square of 1.96 divided by 0.04. The final answer is 507.1.