Problem 6-4: Diners Delight (
and R Charts)
and R Charts)
The management of
the Diners Delight franchised restaurant chain is in the process of
establishing quality-control charts for the time that its service people give
to each customer. Management thinks the length of time that each customer is
given should remain within certain limits to enhance service quality.
A sample of six
service people was selected, and the customer service they provided was
observed four times. The activities that the service people were performing
were identified, and the time to service one customer was recorded as noted
below:
|
Service
Person
|
Sample
1
|
Sample
2
|
Sample
3
|
Sample
4
|
|
1
|
200
|
150
|
175
|
90
|
|
2
|
120
|
85
|
105
|
75
|
|
3
|
83
|
93
|
130
|
150
|
|
4
|
68
|
150
|
145
|
175
|
|
5
|
110
|
90
|
75
|
105
|
|
6
|
115
|
65
|
115
|
125
|
a)
Copy
and paste the data from the table above into Excel. Do the calculations in
Excel and develop and R Charts showing the LCL and UCL. Copy and paste the
spreadsheet calculations and theand R Charts below. Hint: The sample size is six since each
sample contains six observations.
and R Charts showing the LCL and UCL. Copy and paste the
spreadsheet calculations and theand R Charts below. Hint: The sample size is six since each
sample contains six observations.
b.
After
the control chart was established, a sample of six service personnel was
observed, and the following customer service times in seconds were recorded:
180, 125, 110, 98, 156, and 190. Is corrective action called for?
Problem 6-7: Speedway
Clinical Laboratory
The
Speedway Clinical Laboratory is a scientific blood-testing facility that
receives samples from local hospitals and clinics. The blood samples are passed
through several automated tests, and the results are printed through a central
computer that reads and stores the information about each sample that is
tested.
Management
is concerned about the quality of the service it provides and wants to establish
quality-control limits as a measure for the quality of its tests. Such
managerial practice is viewed as significant, because incorrect analysis of a
sample can lead to a wrong diagnosis by the physician, which in turn might cost
the life of a patient. For this reason, 100 blood samples were collected at
random each day after they had gone through testing. After retesting was
performed manually on this sample, the results were:
|
Day
|
Incorrect Analysis
|
Day
|
Incorrect Analysis
|
|
1
|
8
|
11
|
4
|
|
2
|
3
|
12
|
6
|
|
3
|
1
|
13
|
5
|
|
4
|
0
|
14
|
10
|
|
5
|
4
|
15
|
2
|
|
6
|
2
|
16
|
1
|
|
7
|
9
|
17
|
0
|
|
8
|
6
|
18
|
6
|
|
9
|
3
|
19
|
3
|
|
10
|
1
|
20
|
2
|
a)
Copy
and paste the data from the table above into Excel. Do the calculations in
Excel and develop the p chart with the LCL and UCL. Copy and paste the
spreadsheet calculations and the p chart below.
b)
Later,
another sample of 100 was taken. After the accuracy of the tests was
established, 10 samples were found to have been analyzed incorrectly. What is
your conclusion about the quality of this service?
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