In an effort to reduce customer dissatisfaction with delays in replacing lost automated teller machine

(ATM) cards, some retail banks monitor the time required to replace a lost ATM card. Called replacement cycle time, it is the elapsed time from when the customer contacts the bank about the loss until the customer receives a new card (Mnnagement Science, Sept. 1999).

A particular retail bank monitors replacement cycle time for the first five requests each week for replacement cards. Variation in cycle times is monitored usin2 an R-chart. Data for 20 weeks is presented on page 681.

a. Construct an R-chart for these data.

b. What does the R-chart suggest about the presence of special causes of variation in the process?

c. Should the control limits of your R-chart be used to monitor future replacement cycle times? Explain.

d. Given your conclusion in part b and the pattern displayed on the R-chart, discuss the possible future impact on the performance of the bank.