A 24-hour grocery chain would like to formalize their policy regarding how many checkout lines to have open at various times. Clearly, at 2:00 a.m. there is little reason to have more than one open, while on "heavy traffic" days such as the afternoon prior to Thanksgiving, several lines need to be open in order to reduce customer waiting time and congestion within the checkout area.

On the other hand, if too many lines are opened, the additional checkout personnel required to staff the lines have to be taken from other equally critical jobs such as stocking and check cashing. Something has to be done, for right across the street is a large competitor who is poised to take your business if customers find your checkout process too much of an inconvenience.

The management of the chain has proclaimed that no new personnel can be hired just for checkout, unless absolutely necessary. However, they have set an objective that the "average waiting time" that a customer experiences for the entire checkout process (waiting in line plus time for checkout itself) is not to exceed 10 minutes. How then would you go about designing a strategy that provides the store managers with greater insight into how they might better schedule the opening and closing of their checkout lines?

What about opening another "express lane?" Should the latter be restricted to 10 items or fewer? How about 15 or fewer? Does it make a serious difference? And if the company president makes a surprise visit at 1:30p.m. on a Friday, and if there are three checkout lines open, what is the probability that he will have to wait in line no longer than 5 minutes?