Asked by Jasmine

A simple random sample of 50 adults was surveyed, and it was found that the mean amount of time that they spend surfing the Internet per day is 54.2 minutes, with a standard deviation of 14.0 minutes. What is the 99% confidence interval for the number of minutes that an adult spends surfing the Internet per day?
Answered by PsyDAG
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.005) and its Z score = 2.575.

99% = mean ± 2.575 SEm

SEm = SD/√n