1. A. 20% Customers at the Supermarket have a choice when paying for their groceries. They may check out and pay using the standard cashier-assisted checkout, or they may have used the new self-service procedure. In the standard procedure, employee scans each item and puts it in a bag. In the self-service procedure, the customer scans each item and bags it themselves. The self-service procedure is designated to reduce the time a customer spends in the checkout line. The store manager would like to know if the mean checkout time using the standard checkout method is longer than using the self-service. She gathered the following sample information. The time is measured from the customer enters the line until all his or her groceries are in the bags. Hence the time includes both waiting in line and checking out. Customer type Sample size Sample mean Population standard deviation Standard Determine whether self-service procedure is faster or not