Discussion:
Q1. At the time she was hired as a server at the Grumney Family restaurant, Beth Brigden was told, "You can average at least $20 a day in tips." Over the first 35 days she was employed at the restaurant, the mean daily amount of her tips was $24.85, with a standard deviation of $3.24. Can Ms. Brigden be 99% confident that she is earning an average of $20 or more per day in tips?
Q2. The MacBurger restaurant chain claims that the waiting time of customers for service is normally distributed, with a mean of 3 minutes and a standard deviation of 1 minute. The quality-assurance department found in a sample of 50 customers at the Warren Road MacBurger that the mean waiting time was 2.75 minutes. At the 0.05 significance level, can we conclude that the mean waiting time at the Warren Road MacBurger is less than 3 minutes?
Q3. The National Safety Council reported that 52 percent of American turnpike drivers are men. A sample of 300 cars traveling southbound on the New Jersey Turnpike yesterday revealed that 170 were driven by men. At the 0.01 significance level, can we conclude that a larger proportion of men were driving on the New Jersey Turnpike that the national statistics indicate?
Q4. Chicken Delight claims that 90 percent of its orders are delivered within 10 minutes of the time the order is placed. A sample of 100 orders revealed that 82 were delivered within the promised timeframe. At the 0.10 significance level, can we conclude that less than 90 percent of the orders are delivered in 10 minutes or less?