# The manager of a chain of coffee shops is interested in determining if there has been a decrease in

The manager of a chain of coffee shops is interested in determining if there has been a decrease in the mean drive-through service time at his store on weekdays between 6 and 10 a.m. has decreased since the introduction of a new ordering technology that allows customers to see as well as hear the drive through attendant on a screen next to the menu. Here, “service time” is the elapsed time, in seconds, between when the customer finishes ordering and when he or she receives the order from the window.

The manager goes through the point-of-sale data and randomly selects 46 orders from the weekday 6-10 a.m. shift before the time before the technology was implemented (Group 1) and 46 service times for this time period after it was implemented (Group 2). The mean service time before implementation was 233 with a standard deviation of 28, while the mean service time after implementation was 238 with a standard deviation of 24. Calculate the test statistic for testing the hypothesis described above, to two decimal places.