1. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Chapter 16
Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright (c) 2013  John Wiley & Sons, Inc.

2. Learning Objectives Chapter 16
Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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3. 16.1 Acceptance Sampling by Variables
Advantages
Primary advantage of variables sampling plans is that the same operating-characteristic curve can be obtained with a smaller sample size than would be required by an attributes sampling plan
Second advantage is that measurement data usually provide more information than attributes data
Final point is that when acceptable quality level as are very small, sample sizes required by attributes sampling plans are very large
Disadvantages
Distribution of OC curve must be known
Most standard plans assume distribution of quality characteristic is normal
A separate sampling plan must be employed for each quality characteristic that is being inspected
Possible to reject a lot even though the actual sample inspected does not contain any defective items
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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4. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright (c) 2013  John Wiley & Sons, Inc.

5. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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6. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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7. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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8. Cautions in the use of variables sampling:
Usual assumption is that the parameter of interest follows the normal distribution
If parameter of interest is not normally distributed, estimates of the fraction defective will not be the same as if normally distributed
Difference between estimated fraction defectives may be large when dealing with very small fractions defective
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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9. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright (c) 2013  John Wiley & Sons, Inc.

10. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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11. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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12. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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13. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright (c) 2013  John Wiley & Sons, Inc.

14. 16.3 MIL STD 414 (ANSI/ASQ Z1.9)
MIL STD 414 is a lot-by-lot acceptance-sampling plan for variables
Focal point is the AQL which ranges from 0.04% to 15%
Five general inspection levels
Sample sizes are a function of the lot size and the inspection level
Provision is made for normal, tightened, and reduced inspection
Quality characteristic of interest is assumed to be normally distributed
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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15. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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16. Refer to the textbook, page 696 for Table 16.2
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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17. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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18. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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19. Discussion
It is not possible to move directly from an attributes sampling plan in the current MIL STD 105E to a corresponding variables plan in MIL STD 414 if the assurance of continued protection is desired for certain lot sizes and AQLs
Civilian counterpart of MIL STD 414 restores the match to attributes plans—that is, ANSI/ASQC Z1.9 is directly compatible with MIL STD 105E
Makes it possible to start inspection by using an attributes scheme from MIL STD 105E, collect sufficient information to use variables inspection, then switch to variables scheme while maintaining the same AQL-code letter combination
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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20. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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21. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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30. 16.6.2 Other Continuous-Sampling Plans
Variations to the original Dodge CSP-1 have been designed to meet objections
Dodge and Torrey (1951) proposed plans to meet the objection that the occurrence of a single isolated defective unit sometimes does not warrant return to 100% inspection
Lieberman and Solomon (1955) have designed multi-level continuous-sampling plans to overcome the abrupt transition between sampling inspection and 100% inspection
Much of the work has been incorporated into MIL STD 1235C
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31. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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37. Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright (c) 2013  John Wiley & Sons, Inc.