Suppose we want to estimate the expected average waiting time for the first customers at a bank. We make independent replications of the system, each initialized empty and idle and consisting of 100 waiting times. The resulting replicate means are: i 1 2 3 4
Zi 5.2 4.3 3.1 4.2

Required:
Find a 90% confidence interval for the mean average waiting time for the first 100 customers.