quality engineering
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Assignment2.pdf
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MEM 504: Quality Engineering
Assignment # 2
Weight: 5%
Question 1: A manufacturer of wood screws periodically examines screws heads for the presence or
absence of burrs. Subgroups of 300 screws are selected and examined using a carefully designed
procedure. The collected data is as follows:
Observation Number of Screws with Burrs
1 19
2 16
3 11
4 6
5 22
6 2
7 4
8 7
9 5
10 27
11 7
12 13
13 17
14 29
15 1
16 2
17 19
18 28
19 24
20 23
a- Find the centerline (show your calculations) b- Find the control limits (show your calculations) c- Use MINITAB to develop the appropriate control chart d- Are there any special causes of variation? Which observations? e- What to do next?
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Question 2: A given model of large radar dish represents the area of opportunity in which
nonconformities may occur. Results of quality check for 25 radar assemblies are as follows:
Radar Assembly Number Number of Nonconformities
1 25
2 60
3 28
4 65
5 91
6 56
7 40
8 54
9 90
10 44
11 62
12 81
13 70
14 75
15 24
16 50
17 70
18 56
19 21
20 88
21 34
22 82
23 53
24 102
25 64
a- Determine the centerline (show your calculations) b- Determine the control limits (show your calculations) c- Use MINITAB to develop the appropriate control chart d- Are there any indications of lack of control? e- What to do next?
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Question 3: Workers at a packaging operation shovels a granular product from a large pile into sacks
that are then sealed and placed on pallets for shipping. A sequence of 25 subgroups each consisting of
the weights of 5 sacks has been recorded as follows:
Observations
Subgroup # Sack 1 Sack 2 Sack 3 Sack 4 Sack 5
1 35.4 35.6 34.8 34.7 34.8
2 36 35.6 34.9 34.8 35.9
3 35.2 35 35 35.4 35.1
4 34.8 35.8 35.2 35 34.9
5 34.2 35 36.1 34.9 35.1
6 36 35 35.2 34.8 34.9
7 36.1 34.9 34.5 35 35.1
8 35.1 35 35.6 34.9 36.2
9 35 35.6 36.1 34.8 35.6
10 35.4 35.8 36 34.2 36
11 35.2 35.3 35.2 35.9 34.8
12 35.9 36 35.1 35.1 35.6
13 35.2 35.6 35 34.9 35
14 35.2 35.6 35.8 35 35.1
15 34.9 34.8 35 35.2 34.9
16 35.2 35.3 35.2 35.6 35.1
17 35.6 35.8 35.2 35.4 34.9
18 35.2 35.6 35.4 35.6 35.2
19 34.7 34.9 35.6 35.2 35
20 35 35.1 35.6 35 35.1
21 35.6 35 35.8 35.2 34.6
22 34.9 35.1 35.6 35 35.2
23 35.9 36 35.2 36 35.2
24 35.2 35.1 35.4 34.9 35.1
25 35.2 35.2 35.1 35.6 34.9
a- What is the appropriate control chart that can be used by the quality engineer in this case? b- Determine the control limits (show your calculations) c- Construct the appropriate control chart for the data above using MINITAB. d- Is the process in-control? If not, when does the out-of-control behavior occur? e- If the process is found to be out of control, drop the out-of-control points and use MINITAB to
re-construct the control chart.
f- Is the process now in-control? If not, what to do next?
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Question 4: Viscosity is one of the important quality characteristics of paste ink used in printing presses.
A viscosity measure is taken at the end of production of each batch of ink. Viscosity measures for 50
consecutive batches have been recorded as follows:
Sample Viscosity Sample Viscosity
1 305 26 291
2 274 27 301
3 290 28 290
4 314 29 290
5 291 30 308
6 315 31 306
7 301 32 292
8 298 33 279
9 306 34 276
10 305 35 285
11 270 36 296
12 296 37 275
13 307 38 299
14 284 39 301
15 280 40 294
16 264 41 312
17 299 42 289
18 270 43 278
19 275 44 288
20 276 45 299
21 294 46 270
22 313 47 308
23 304 48 298
24 310 49 294
25 271 50 306
a- What is the appropriate control chart that can be used by the quality engineer in this case? b- Determine the control limits (show your calculations) c- Construct the appropriate control chart for the data above using MINITAB. d- Is the process in-control? If not, when does the out-of-control behavior occur? e- If the process is found to be out of control, drop the out-of-control points and use MINITAB to
re-construct the control chart.
f- Is the process now in-control? If not, what to do next?
