Case Problem $3\mathrm{.}3$

Improving Service Time at Dave$$s Burgers

Dave$$s Burgers is a fast$-$food restaurant franchise in Georgia, South Carolina, and North Carolina. Recently, Dave$$s Burgers has followed the lead of larger franchise restaurants like Burger King, McDonald$$s$,$ and Wendy$$s and constructed drive$-$through windows at all its locations. However, instead of making Dave$$s Burgers more competitive, the drive$-$through windows have been a source of continual problems, and it has lost market share to its larger competitors in almost all locations. To identify and correct the problems, top management has selected three of its restaurants $($one in each state$)$ as test sites and has implemented a quality management program at each of them. At the Charlotte, North Carolina, test restaurant, a quality team made up of employees, managers, and quality specialists from company headquarters, using traditional quality tools like Pareto charts, checksheets, fishbone diagrams, and process flowcharts, have determined that the primary problem is slow, erratic service at the drive$-$through window. Studies show that the time a customer arrives at the window to the time the order is received averages $2\mathrm{.}6$ minutes. To be competitive, management believes service time should be reduced to at least $2\mathrm{.}0$ minutes and ideally $1\mathrm{.}5$ minutes.

The Charlotte Dave$$s Burgers franchise implemented a number of production process changes to improve service time at the drive$-$through window. It provided all employees with more training across all restaurant functions, improved the headset system, improved the equipment layout, developed clearer signs for customers, streamlined the menu, and initiated even$-$dollar $($tax$-$inclusive$)$ pricing to speed the payment process. Most important, the restaurant installed large, visible electronic timers that showed how long a customer was at the window. This not only allowed the quality team to measure service speed but also provided employees with a constant reminder that a customer was waiting.

These quality improvements were implemented over several months, and their effect was immediate. Service speed was obviously improved, and market share at the Charlotte restaurant increased by $5\%.$ To maintain quality service, make sure the service time remained fast, and continue to improve service, the quality team decided to use a statistical process control chart on a continuing basis. They collected six service time observations daily over a $15-$day period, as follows:

Case $3\mathrm{.}3$

Construct a control chart to monitor the service at the drive$-$through window. Determine if your control chart can be implemented on a continuing basis or if additional observations need to be collected. Explain why the chart you developed can or cannot be used. Finally, discuss what other statistical process control charts Dave$$s Burgers might use in its overall quality$-$management program.