## Elementary Statistics (12th Edition)

E=0.022, $\hat{p}=0.85$. Hence $E_{1}=\frac{z_{\alpha}}{z_{\frac{\alpha}{2}}}\cdot E=\frac{1.645}{1.96}\cdot 0.22=0.019.$ Hence, the confidence interval: p is more than $\hat{p}-E$ or less than $\hat{p}+E$, hence p is more than 0.85-0.019=0.831 or less than 0.85+0.019=0.869.