Question

McDonald's is concerned that its lunchtime drive-thru customer orders are taking too long to complete. They decide to randomly choose five (5) lunchtime drive-thru orders per day for five (5) days. The service times for each order are provided in the table below. You are to use 3 sigma control limits and assume that an R-chart is not appropriate because management desires greater precision in the variation calculations. Select the appropriate control chart type(s) as taught in class (don’t forget the labels) and use two (2) decimal places in your calculations. Show your control limit calculations and state whether or not this process is in or out of control and why!

McDonald's Drive-Thru Order Times (In Minutes)
Day	Order 1	Order 2	Order 3	Order 4	Order 5
1	11	13	5	7	8
2	6	10	8	6	5
3	8	5	5	6	12
4	5	4	9	10	7
5	7	6	7	7	14

- Chart - Chart 12 3 4 5

Answer 1

Solution:
Please find the image attached for a more detailed solution:

All the processes are in control variation as evident from the chart shown in the image because the process lies within the control limits which are designed for this control chart.

Day Order 1 Order 2 Order 3 Order 4 Order 5 Range Mean (X_bar) UCL LCL 13 8.8 0.577 11.56 3.72 6 10 12 6 10 7.2 UCL X_bar_bar A2 R bar LCL Xbar_bar - A2 * R_bar 6 8.2 7.64 X bar bar 6 14 6.8 R bar Average A2 for number of samples equalto 5 is 0.577 X-bar-bar Chart 14 12 10 2 -Mean (X-bar) -UCL -LCL