The file P02_16.xlsx contains traffic data from 256 weekdays on four variables. Each variable lists the number of arrivals during a specific 5-minute period of the day. For this problem, consider this data set a simple random sample from all possible weekdays.
a. For each of the four variables, find the sample mean. If each of these is used as an estimate from the corresponding (unknown) population mean, is there any reason to believe that they either underestimate or overestimate the population means? Why or why not?
b. What are the (approximate) standard errors of the estimates in part a? How can you interpret these standard errors? Be as specific as possible.
c. Is it likely that the estimates in part a are accurate to within 0.4 arrival? Why or why not?