Confidence interval for the true proportion

Question

out of 600 people sampled 516 receive flu vaccinations this year based on those construct 99% confidence interval for the true population proportion of people who received the flu vaccinations this year

___ < p < ____

Answer 1

CI = phat +/- z-critical * SE

where z-critical for 99 confidence level is 2.58

phat = 516/600 = 0.86

SE = sqrt(phat * (1-phat)/sample size) = sqrt(0..86*0.14/600) = 0.014

so CI = 0.86 +/- 2.58 * 0.014 = 0.82, 0.90