1. Solutions to Chapter 3 Exercises
Chapter 3: Quality Management

2. Chapter 3: Quality Management
Exercise 1
Chapter 3: Quality Management

3. Chapter 3: Quality Management
Exercise 2
Chapter 3: Quality Management

4. Chapter 3: Quality Management
Exercise 2 continued
The upward trend in cancellations and non-renewals is a definite cause for concern.
Chapter 3: Quality Management

5. Chapter 3: Quality Management
Exercise 3
Chapter 3: Quality Management

6. Chapter 3: Quality Management
Exercise 3 concluded
1.2826
1.02
.7574
UCL * * * * * *
LCL
Jun Jul Aug Sep Oct Nov
Chapter 3: Quality Management

7. Chapter 3: Quality Management
Exercise 4 Xi
3,500
4,100
3,750
4,300
4,000
3,650
Total 23,300
Chapter 3: Quality Management

8. Chapter 3: Quality Management
Exercise 5
Chapter 3: Quality Management

9. Chapter 3: Quality Management
Exercise 5 concluded
Normally control limits are set at three sigma so any point outside the limits is to be investigated. For limits set at lower sigma values, it should be considered that there is a chance of a random point falling outside the limits even though the process is in control. For one-sigma limits the chance is 32% or one out of three points. For two-sigma limits the chance is 5%, or one point out of twenty. In our case there are 3 points out of twelve, so action should be taken, but if these had been one-sigma limits, action would be unnecessary.
Chapter 3: Quality Management

10. Chapter 3: Quality Management
Exercise 6a
Day Range
Sat
Sun
Mon
Tue
Wed
Thu
Sum
For Friday the range is 7, so the range on Friday is in control.
Chapter 3: Quality Management

11. Chapter 3: Quality Management
Exercise 6a concluded
9.45
3.67
UCL * * * * * * *
LCL
Sat Sun Mon Tue Wed Thu Fri
Chapter 3: Quality Management

12. Chapter 3: Quality Management
Exercise 6b
Day Sample Mean
Sat
Sun
Mon
Tue
Wed
Thu
Sum
For Friday the sample mean is 16.7, so the process is in control.
Chapter 3: Quality Management

13. Chapter 3: Quality Management
Exercise 6b concluded
22.96
19.21
15.45
UCL * * * * * * *
LCL
Sat Sun Mon Tue Wed Thu Fri
Chapter 3: Quality Management

14. Exercise 7
Dough Boy’s pizza crust production system is not capable of consistently meeting its customer requirements given the Cp index of less than 1. Options available to Dough Boy include improving its production system to lower the natural variation in the system. In this case, Dough Boy needs to reduce the standard deviation of pizza crusts from 1.1 to .66 or lower in order to obtain a Cp index of 1 or more. Alternatively, Dough Boy could try to convince its customers to increase the range of acceptable pizza crust diameters.

15. Chapter 3: Quality Management
Exercise 8
The Cp index indicates that given the natural variation in the filling operation, it is capable of meeting the design specifications. However, when the alignment of the process mean and the design specification is considered, it is found that the filling operation is not capable of consistently meeting design requirements.
Chapter 3: Quality Management

16. Chapter 3: Quality Management
Exercise 9a
Total number of cases = 27,400
Total incorrect = 235
Chapter 3: Quality Management

17. Chapter 3: Quality Management
Exercise 9a concluded
.03623
.00857
0.0
UCL
LCL
Chapter 3: Quality Management

18. Chapter 3: Quality Management
Exercise 9b: Day 7
On day 7, p = .0115, therefore process is in control.
Chapter 3: Quality Management

19. Chapter 3: Quality Management
Exercise 9b: Day 8
On day 8, p = .0093, therefore process is in control.
Chapter 3: Quality Management

20. Chapter 3: Quality Management
Exercise 9b: Day 9
On day 9, p = .0123, therefore process is in control.
Chapter 3: Quality Management

21. Chapter 3: Quality Management
Exercise 10
X p c
Mon
Tue
Wed
Sum
Avg
Chapter 3: Quality Management

22. Exercise 10: Sample Means Chart
A2 = 1.023; Range = 19
UCL = (19) = 45.44
LCL = (19) = 6.56
Thursday’s 47 defectives is outside control limits.
Chapter 3: Quality Management

23. Chapter 3: Quality Management
Exercise 10: p chart
On Thursday, p = , therefore not in control.
Chapter 3: Quality Management

24. Chapter 3: Quality Management
Exercise 10: c chart
On Thursday, 47 are defective. Thus, out of control.
Chapter 3: Quality Management

25. Chapter 3: Quality Management
Exercise 10 concluded
The c chart is most appropriate
The p chart is acceptable
The sample means chart is not appropriate
Chapter 3: Quality Management