Answer:
CI = x ± 2.58 (s / √n)
Explanation:
The confidence interval is the mean plus or minus the margin of error. The margin of error is the critical value times the standard error. For a normal distribution, the critical value is the z-score at the given confidence level. The standard error is the standard deviation divided by the square root of the sample size.
CI = x ± z (s / √n)
At 99% confidence, z = 2.58.
CI = x ± 2.58 (s / √n)