Quality Management Statistics.
1. For a process quality characteristics, the specification limits are 0.4037 +/- 0.0013 (that is from 0.4024 to 0.4050). The following data gives the data for 14 measurement data sets, each data set is a subgroup of 5 measurement. The value is recorded in the units of 0.0001 (that is, the specification limit will be considered 24 to 50) Based on the following data, compute Cp,Cpk,Pp and Ppk.(Use MINITAB is ok) and determine if the capability of the process.
|
Subgroup # |
1 |
2 |
3 |
4 |
5 |
Subgroup # |
1 |
2 |
3 |
4 |
5 |
|
1 |
36 |
35 |
34 |
33 |
32 |
8 |
34 |
38 |
35 |
34 |
38 |
|
2 |
31 |
31 |
34 |
32 |
30 |
9 |
36 |
35 |
37 |
34 |
33 |
|
3 |
30 |
30 |
32 |
30 |
32 |
10 |
30 |
37 |
33 |
34 |
35 |
|
4 |
32 |
33 |
33 |
32 |
35 |
11 |
28 |
31 |
33 |
33 |
33 |
|
5 |
32 |
34 |
37 |
37 |
35 |
12 |
33 |
30 |
34 |
33 |
35 |
|
6 |
32 |
32 |
31 |
33 |
33 |
13 |
35 |
36 |
29 |
27 |
32 |
|
7 |
33 |
33 |
36 |
32 |
31 |
14 |
33 |
35 |
35 |
39 |
36 |
2. The following table listed 25 subgroups of measurement data with group size 3:
|
# |
c1 |
c2 |
c3 |
# |
c1 |
c2 |
c3 |
|
1 |
50.3175 |
50.1224 |
50.4081 |
14 |
49.4319 |
50.1432 |
49.2045 |
|
2 |
49.5077 |
49.7629 |
49.4091 |
15 |
50.3789 |
50.2715 |
50.5952 |
|
3 |
49.3587 |
49.639 |
49.5229 |
16 |
48.6722 |
49.1436 |
49.1306 |
|
4 |
49.5005 |
49.5897 |
49.7904 |
17 |
49.5332 |
50.4829 |
50.0007 |
|
5 |
47.911 |
49.5549 |
48.6716 |
18 |
49.4866 |
47.9221 |
50.4324 |
|
6 |
49.8851 |
49.8281 |
49.8762 |
19 |
48.6924 |
50.1697 |
49.8926 |
|
7 |
49.9994 |
50.6484 |
50.4223 |
20 |
50.8253 |
50.7303 |
50.8569 |
|
8 |
49.58 |
49.4764 |
49.7899 |
21 |
50.3306 |
49.8906 |
49.5988 |
|
9 |
51.106 |
50.2333 |
50.4464 |
22 |
49.9728 |
51.6716 |
50.7228 |
|
10 |
50.7538 |
49.9355 |
51.4371 |
23 |
50.5934 |
50.7355 |
49.3386 |
|
11 |
49.7322 |
49.6442 |
50.2943 |
24 |
49.5547 |
49.7753 |
49.7181 |
|
12 |
48.5373 |
51.9875 |
48.6112 |
25 |
51.3211 |
48.048 |
51.7502 |
|
13 |
48.6753 |
48.9048 |
49.3312 |
|
|
|
|
(a) The specification limits are 49 +/- 3. Assume that the data is normally distributed! Estimate process capability ratio’s (Cp, Cpk, Pp, Ppk). Is the process capable?
(b) If the specification limits were 51 +/- 3. Re-calculate process capability ratio’s (Cp, Cpk, Pp, Ppk). Is the process still capable?
(c) Comment on the difference between Cp and Cpk ratios.