A poll of 811 adults aged 18 or older asked about purchases that they intended to make for the upcoming holiday season. One of the questions asked about what kind of gift they intended to buy for the person on whom they will spend the most. Clothing was the first choice of 487 people. Give a 99% confidence interval for the proportion of people in this population who intend to buy clothing as their first choice.

Question

p0sitr0n · Answer

if the interval is two sided, then you need $$I=\hat{p} \pm Z_{0.005}\sqrt{\frac{\hat{p}\hat{q}}{n}}$$