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Statistical Methods for Quality Improvement, Third Edition by THOMAS P. RYAN

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Answers to Selected Exercises

Chapter 2

  • 1. 9

Chapter 3

  • 1. S2 = 7.3. Adding a constant to every number in a sample does not change the value of S2.
  • 5. (a) 0.95053; (d) 0.9545; (e) z0 = 1.96.
  • 7. images.
  • 9. 0.06681. The probability is approximate since the particular probability distribution was not stated.
  • 15. 2. We have 3% as the estimate of the proportion nonconforming, and conclude that the process needs improving.
  • 17. 0.9727.
  • 22. (c)

Chapter 4

  • 5. The control limits could be adjusted or a control chart of residuals could be used.
  • 20. 80.5

Chapter 5

  • 2. 13, 2.
  • 3. The moving ranges and moving averages are correlated so interpreting the charts can be difficult.
  • 5. An images chart is more sensitive in detecting a shift in the process mean (as the answers to exercise 2 indicate).

Chapter 6

  • 1. 0.0462 and 0.2583.
  • 3. Because there will not be a lower control limit.

Chapter 7

  • 3. (a) images; (c) decrease, 0.02278 (before), 0.0027 (after).
  • 5. 1.479, no.

Chapter 8

  • 2. (a) 5.75 assuming a basic CUSUM scheme; (b) 15.
  • 3. When doubt exists as to whether or not an assignable cause was removed.

Chapter 9

  • 1. (a) 11.58.

Chapter 11

  • 2. (a) No outliers are identified; (b) the estimate of sigma is 3.21.

Chapter ...

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