Question: A local video store owner is concerned that most of his customers are switching to NETFLIX for their movie watching. To combat this he starts a real-time delivery program where customers can order online, get a movie by taxi and then return it the next day. A sample of 20 test subjects results in a sample average of 6.5 minutes delivery time with a sample standard deviation of 1.3 minutes. With 95% confidence, what can the owner say about his delivery time? What assumptions did he have to make about his data?