A publisher wants to estimate the mean length of time (in minutes) all adults spend reading newspapers. To determine this estimate, the publisher takes a random sample of 15 people and obtains the results below. From past studies the publisher assumes the standard deviation is 2.5 minutes and that the population of times is normally distributed.
6, 7, 8, 12 , 9, 7, 6, 12, 12, 10, 8, 8, 11, 6, 11
1. What is the the 90% confidence interval?
2. What is the 99% confidence interval?
3.Is the 90% or the 99% confidence interval wider? Answer: the 99% (?)