The file P08_06.xlsx contains data on repetitive task times for each of two workers. John has been doing this task for months, whereas Fred has just started. Each time listed is the time (in seconds) to perform a routine task on an assembly line. The times shown are in chronological order.
a. Find a 95% confidence interval for the mean time it takes John to perform the task. Do the same for Fred.
b. Do you believe both of the confidence intervals in part a are valid and/or useful? Why or why not? Which of the two workers would you rather have, assuming that task time is the only issue?