A company running an urban rail service wishes to estimate its daily average number of late-running trains on weekdays. For 10 randomly selected weekdays, it finds the following numbers of late running trains:
32, 10, 9, 18, 25, 15, 14, 18, 22, 16
- a) Assuming the number of late running trains on a weekday is approximately normally distributed, calculate a 90% confidence interval for the mean number of late-running trains on a weekday.
- b) If we did not have the assumption of normality, could we still calculate a confidence interval in this example? If not, suggest a way of overcoming this problem.
