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Replacement times for lost ATM cards. In an effort to
Chapter 13, Problem 34E(choose chapter or problem)
Replacement times for lost ATM cards. 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 (Management 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 using an R-chart. Data for 20 weeks are presented below.
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.
Questions & Answers
QUESTION:
Replacement times for lost ATM cards. 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 (Management 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 using an R-chart. Data for 20 weeks are presented below.
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.
ANSWER:Step 1 of 7
a) We need to construct R chart for the given widths.
The formulas used in construction of R-chart are as shown below:
Where,
k is the number of samples.
Use MINITAB using the following instruction set as follows:
1) Type or Import data in columns representing widths Timel, Time2, Time3,
Time4, Time5.
2) Select R bar... from the Variable Charts for Subgroups in Control Charts
of Stat ribbon.
3) Specify Length for “Observations of subgroups are in one row of
columns”.
4) Check all the tests for the special causes in Tests ribbon of R bar Options…
tab, then click estimates and check the R bar.
5. Click Ok.