Answer
$0.76\pm0.0343$
Work Step by Step
$\hat{p}=0.76$
The z-value belonging to the $90\%$ confidence interval according to the table is $z=1.64$, thus the confidence interval is: $\hat{p}\pm z\sqrt{\frac{p(1-p)}{n}}$, which here is: $0.76\pm 1.64\sqrt{\frac{0.76\cdot(1-0.76)}{418}}=0.76\pm0.0343$
