Construct a 90% confidence interval estimate of the average amount of time that is saved for managers spending time on email as a result of the new procedures described in Exercise 6.
A large accounting firm is concerned about the amount of time its managers spend dealing with email. A random sample of 27 managers taken in the past revealed that they spent, on average, 49.2 minutes per day on email, with a standard deviation of 22.3 minutes. Since then, new procedures have been put in place. Another random sample of 25 managers reveals that they spent, on average, 39.6 minutes per day on email, with a standard deviation of 10.6 minutes. Is there evidence, at the 5% level of significance, that the new procedures have reduced the amount of time managers spend on email? You may assume that the sample data sets appear normally distributed.