The data in Table 7E.19 are the number of information errors found in customer records in a marketing company database. Five records were sampled each day.
(a) Set up a c chart for the total number of errors. Is the process in control?
(b) Set up a t chart for the total number of errors, assuming a geometric distribution with a = 1. Is the process in control?
(c) Discuss the findings from parts (a) and (b). Is the Poisson distribution a good model for the customer error data? Is there evidence of this in the data?
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TABLE 7 E .19
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Customer Error Data for Exercise 7.67
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|
Day
|
Record 1
|
Record 2
|
Record 3
|
Record 4
|
Record 5
|
|
1
|
8
|
7
|
1
|
11
|
17
|
|
2
|
11
|
1
|
11
|
2
|
9
|
|
3
|
1
|
1
|
8
|
2
|
5
|
|
4
|
3
|
2
|
5
|
1
|
4
|
|
5
|
3
|
2
|
13
|
6
|
5
|
|
6
|
6
|
3
|
3
|
3
|
1
|
|
7
|
8
|
8
|
2
|
1
|
5
|
|
8
|
4
|
10
|
2
|
6
|
4
|
|
9
|
1
|
6
|
1
|
3
|
2
|
|
10
|
15
|
1
|
3
|
2
|
8
|
|
11
|
1
|
7
|
13
|
5
|
1
|
|
12
|
6
|
7
|
9
|
3
|
1
|
|
13
|
7
|
6
|
3
|
3
|
1
|
|
14
|
2
|
9
|
3
|
8
|
7
|
|
15
|
6
|
14
|
7
|
1
|
8
|
|
16
|
2
|
9
|
4
|
2
|
1
|
|
17
|
11
|
1
|
1
|
3
|
2
|
|
18
|
5
|
5
|
19
|
1
|
3
|
|
19
|
6
|
15
|
5
|
6
|
6
|
|
20
|
2
|
7
|
9
|
2
|
8
|
|
21
|
7
|
5
|
6
|
14
|
10
|
|
22
|
4
|
3
|
8
|
1
|
2
|
|
23
|
4
|
1
|
4
|
20
|
5
|
|
24
|
15
|
2
|
7
|
10
|
17
|
|
25
|
2
|
15
|
3
|
11
|
2
|