Statistics construct a 99% confidence interval

Question

If n=310 and  (p-hat) = 0.23, construct a 99% confidence interval.Give your answers to three decimals.

__________- < p < _____________

Answer 1

Formula for confidence interval: phat +/- z-critical * sqrt(phat*(1-phat)/n), where z-critical is value for 99% confidence interval.

z critical = z such that P(z < z-critical) = 0.995 --> z-critical = 2.576.

CI is 0.23 +/- 2.576 * sqrt(0.23 * 0.77/310)