Sixto Sanchez is the owner of Suburban Stylists. He is evaluating the service level provided to walk-in customers. Because he is enrolled in an MBA program at Eastern University, Sixto decides to sample walk-in customers for the next two weeks. He collects information from 82 walk-in customers and calculates that their average waiting times that is 21 minutes with a standard deviation of 4 minutes.
a) Determine the degrees of freedom to be used in further analysis.
b) Calculate the two sided 95% confidence interval for the population mean of waiting times.
c) Calculate the two sided 90% confidence interval for the population mean of waiting times.
d) Calculate the two sided 99% confidence interval for the population mean of waiting times.
e) What t table value should be used in calculating a two sided 95% confidence interval for the population mean of waiting times if the sample selected is 25 instead of 82?