Question: Question 3: The following data set represents the time (in minutes) for a random sample of phone calls made by employees at a company:

(b) Find the sample standard deviation.

(c) Use the t-distribution to construct a 90% confidence interval for the population mean and interpret the results. Assume the population of the data set is normally distributed.

(d) Repeat part (c) assuming that \(\sigma =3.5\). Compare results.