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Informative

1. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
QualityQuality Control Control
Chapter 10- Acceptance Chapter 10- Acceptance
Sampling SystemsSampling Systems
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BesterfieldBesterfield
Quality Control, 8eQuality Control, 8e
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2. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
OutlineOutline
Lot-by-lot acceptance sampling plans for
attributes
Acceptance sampling plans for continuous
production
Acceptance sampling plans for variables

3. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Learning ObjectivesLearning Objectives
When you have completed this chapter you
should be able to:
Determine the sampling plan using ANSI/ASQ
Z1.4.
Know the switching rules for ANSI/ASQ Z1.4.
Categorize the various sampling plan systems in
terms of lot-by-lot, continuous production,
attributes or variables.

4. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Learning Objectives-cont’d.Learning Objectives-cont’d.
When you have completed this chapter you
should be able to:
Describe the various sampling plan systems and
know their function (advantages, disadvantages,
purpose etc.).
Determine the sampling plan using the Dodge
Romig Tables
Construct the OC Curve for a chain sampling plan.

5. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Learning Objectives-cont’d.Learning Objectives-cont’d.
When you have completed this chapter you
should be able to:
Be able to use the Shainin Lot Plot Method.
Determine the sampling plan ANSI/ASQ S1
Determine whether a lot is accepted or rejected
using ANSI/ASQ Z1.9

6. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Lot-by-Lot Acceptance Sampling Lot-by-Lot Acceptance Sampling
Plans for AttributesPlans for Attributes
Devised in 1942 at Bell Labs
Later became MIL-STD-105E
ISO-2859
ANSI/ASQ Z1.4
Wording & terminology changes
Additional tables added

7. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
This standard is applicable to:
End items
Components and raw materials
Operations
Materials in process
Supplies in storage
Maintenance operations
Data or records

8. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
Intended to be used for a continuing
series of lots, but may be designed for
isolated lots.
Standard provides for single, double,
and multiple sampling plans.
Provision is also provided for normal,
tightened, or reduced inspection.
Plan is specified by the AQL, and
sample-size code.

9. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
Normal inspection is used at the start of
inspection with changes being a function of
recent quality history.
Tightened inspection:
Generally used when producer’s recent
quality history has deteriorated.

10. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
Reduced inspection:
Used when the producer’s recent quality
history has been exceptionally good.
Decision concerning what type of plan to
use is left to the responsible authority.
Nonconformities are classified such as
critical, major…

11. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4

12. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Sample Size Code LettersSample Size Code Letters

13. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Comparison of Inspection levelsComparison of Inspection levels
III
1086
Percent Nonconforming (100Pa)
100
95
80
60
40
20
0
100=10
= 0.05
P
e
r
c
e
n
t

o
f

L
o
t
s

A
c
c
e
p
t
e
d

(
1
0
0
P
a
)
42
II I
I = 1/2 n
II = n
III = 2n

14. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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ANSI/ASQ Z1.4ANSI/ASQ Z1.4

AQLAQL
The AQL is the most important part of the
standard since the AQL and sample size
dictate the plan used.
AQL is defined as the maximum percent
nonconforming that can be considered
satisfactory as a process average.
Satisfactory = Producer’s risk, α
Usually 0.05

15. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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ANSI/ASQ Z1.4ANSI/ASQ Z1.4
AQLAQL
AQL is specified by contract or
responsible authority.
AQL may be determine from
historical data, empirical
judgment, engineering
information, experimentation,
producer’s capability, consumer’s
requirements.

16. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4

AQLAQL
AQL is specified by contract or responsible
authority.
AQL may be determine from historical data,
empirical judgment, engineering
information, experimentation, producer’s
capability, consumer’s requirements.
17

17. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
Sample SizeSample Size
Determined by lot size and inspection
level
Use of sample-size code
Inspection level is determined by the
responsible authority.
17

18. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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ANSI/ASQ Z1.4ANSI/ASQ Z1.4

Sample SizeSample Size
Different levels of inspection provide
approximately the same protection to
the producer, but different protections
to the consumer.
Plan provides for “special” levels to be
used where relatively small sample
sizes are necessary and large sampling
risks must be tolerated. (S-1, S-2, S-3, S-
4)
18

19. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Implementation
Determine lot size
Determine inspection level
Find sample-size code letter in table
Determine AQL
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
19

20. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Implementation cont’d.
Determine type of sampling plan
Find sampling plan in appropriate table
Start with normal inspection and
change to tightened or reduced based
on switching rules
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
20

21. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
What an AQL means is that as long as a
supplier maintains his/her process average
(% defective) at the assigned AQL or lower,
there is a very high probability that
shipments from that supplier, when
inspected using ASQ Z1.4 sampling plans,
will be accepted. 
AQLAQL
21

22. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
By the same token, there is a very high
probability that shipments, when inspected
using ASQ Z1.4 sampling plans, will be
rejected if a supplier's process average (%
defective) remains higher than the assigned
AQL.
AQLAQL
22

23. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Single sampling plans
Start by identification of AQL, lot size,
inspection level, and type of sampling
plan.
Locate appropriate plan parameters in
tables.
Double and Multiple Sampling
Similar procedures as single sampling
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
23

24. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Normal, Tightened, and Reduced Inspection
Start with normal inspection
Switching Procedures
Normal to tightened
Institute when 2 out of 5 consecutive lots not
accepted on original inspection
Tightened to normal
Institute when 5 consecutive lots accepted
If not, then discontinue inspection under this plan
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
24

25. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Switching Procedures
Normal to reduced
Institute when: (all of the following)
Preceding 10 lots on normal inspection
have been accepted
Total nonconforming in preceding 10
samples is less than number identified in Table
10-5.
Production is at a steady rate
Reduced inspection is considered desirable
by responsible authority
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
25

26. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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
Switching ProceduresSwitching Procedures

Reduced to normalReduced to normal
Institute when: (any of the following)Institute when: (any of the following)

A lot is not acceptedA lot is not accepted
Sampling procedure terminates with neither Sampling procedure terminates with neither
acceptance or rejection criteria have been acceptance or rejection criteria have been
metmet

Production is irregular or delayedProduction is irregular or delayed

Other conditionsOther conditions
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
26

27. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Standard is designed for use where units of
product are produced in a continuing series of
lots or batches.
If a sampling plan is desirable for a lot or batch of
an isolated nature, it should be chosen based on
the Limiting Quality (LQ) and consumer’s risk, b.
These tables are included in the standard, but
not the textbook.
Or use ANSI/ASQ Standard Q3
ANSI/ASQ Z1.4ANSI/ASQ Z1.4
27

28. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Standard is used for inspection of
isolated lots by attributes.
Provides indexed tables by Limiting
Quality, LQ.
ANSI/ASQ Standard Q3ANSI/ASQ Standard Q3
28

29. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Two Schemes:
1. Used for lots that are isolated or mixed
or that have an unknown history as far as
all parties know.
Lot size and LQ must be known.
Nominal values of the LQ are based
on b=0.10
ANSI/ASQ Standard Q3ANSI/ASQ Standard Q3
29

30. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Two Schemes:
2. Used when a vendor is producing a
continuous stream of lots and sends one
or a few to a customer who will consider
them as isolated lots.
Occurs frequently when purchasing
small quantities of raw materials.
ANSI/ASQ Standard Q3ANSI/ASQ Standard Q3
30

31. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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
A set of inspection tables for lot-by-lot A set of inspection tables for lot-by-lot
acceptance sampling by attributes.acceptance sampling by attributes.

Tables are based on Limiting Quality (LQ) Tables are based on Limiting Quality (LQ)
and Average Outgoing Quality Limit (AOQL).and Average Outgoing Quality Limit (AOQL).

Tables for single and double samplingTables for single and double sampling

Advantage that the plan provides a Advantage that the plan provides a
minimum amount of inspection for a given minimum amount of inspection for a given
inspection procedure.inspection procedure.

Desirable for in-house inspectionDesirable for in-house inspection
Dodge-Romig TablesDodge-Romig Tables
31

32. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Limiting Quality – LQ
Based on the probability that a particular
lot, which has percent nonconforming equal
to the LQ, will be accepted.
Probability is the consumer’s risk, β = 0.10
LQ plans give assurance that individual
lots of poor quality will rarely be
accepted..
Dodge-Romig TablesDodge-Romig Tables
32

33. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Observations about the LQ tables:
As the lot size increases, the
relative sample size decreases.
The tables extend until the process
average is one-half of the LQ.
As the process average increases, a
corresponding increase occurs in
the amount inspected.
Dodge-Romig TablesDodge-Romig Tables
33

34. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Average Outgoing Quality Limit – AOQL
Applicable when the inspected lot is a
convenient subdivision of a flow of
product for materials handling purposes
(non-homogeneous)
AOQL plan limits the amount of poor
outgoing quality on an average basis, but
gives no assurance on individual lots.
Dodge-Romig TablesDodge-Romig Tables
34

35. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Process average
Obtained by the same techniques as for p-charts
First 25 lots the average percent
nonconforming is obtained
Type of nonconformance
Dodge-Romig tables do not provide for different
categories or tightened inspection
Different LQ or AOQL values may be used
Dodge-Romig TablesDodge-Romig Tables
35

36. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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A special type of lot-by-lot acceptance sampling
plan for attributes designated as “Chain
Sampling Plan ChSP-1”.
Applicable to quality characteristics which
involve destructive or costly tests.
Use of small sample sizes
Acceptance number, c=0
Poor shape of OC curve at the producer’s
risk
Chain Sampling Inspection PlanChain Sampling Inspection Plan
36

37. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Chain sampling uses the cumulative results of
several samples
Determination of the value of i, the
number of previous samples, is
determined by analysis of the OC
curves for a given sample size.
Chain Sampling Inspection PlanChain Sampling Inspection Plan
37

38. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Procedure:
For each lot, select a sample of
size n and test each for
conformance to specifications.
Chain Sampling Inspection PlanChain Sampling Inspection Plan
38

39. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Procedure:
If the sample has 0 nonconforming
units, accept the lot; if the sample has 2
or more nonconforming units, do not
accept the lot; and if the sample has 1
nonconforming unit, it may be accepted
provided that there are 0
nonconforming units in the previous
i samples of size n.
Chain Sampling Inspection PlanChain Sampling Inspection Plan
39

40. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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n=5n=5
c=0c=0
LastLast LotLot
Second-Second-
to-Lastto-Last
LotLot
i previous lotsi previous lots
Current LotCurrent Lot
Accept if 0 Nonconforming UnitsAccept if 0 Nonconforming Units
in in n =5n =5 or if or if 11 Nonconforming Unit Nonconforming Unit
&& Zero Nonconforming Units in Zero Nonconforming Units in ii
Previous LotsPrevious Lots
Chain Sampling DiagramChain Sampling Diagram
Figure 10-4 Chain Sampling Diagram
40

41. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Conditions for use of the Chain Sampling
Plan:
1.1.The lot should be one of continuing The lot should be one of continuing
series of product that is sampled in series of product that is sampled in
substantially the order of substantially the order of
productionproduction
2.2.The consumer can normally expect The consumer can normally expect
the lots to be essentially the same the lots to be essentially the same
quality.quality.
Chain Sampling Inspection PlanChain Sampling Inspection Plan
41

42. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Conditions for use of the Chain Sampling
Plan:
3.3.The consumer has confidence in the The consumer has confidence in the
producer not to occasionally send producer not to occasionally send
an unacceptable lot that would have an unacceptable lot that would have
the optimum chance of acceptance.the optimum chance of acceptance.
4.4.The quality characteristic is one that The quality characteristic is one that
involves destructive or costly tests.involves destructive or costly tests.
Chain Sampling Inspection PlanChain Sampling Inspection Plan
42

43. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Used for costly or destructive tests
Subgroup size of 1 – item by item plan
Sequential sampling is similar to multiple
sampling, except sequential sampling can, in
theory, continue indefinitely.
In practice, the plan is truncated after the number
inspected is equal to three times the number
inspected by a corresponding single sampling plan.
Based on the Sequential Probability Ratio Test
Sequential SamplingSequential Sampling
43

44. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Sequential Sampling PlanSequential Sampling Plan
44

45. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Sequential Sampling PlanSequential Sampling Plan
45

46. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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
Designated SkSP-1 and based on AOQL.Designated SkSP-1 and based on AOQL.

A single sampling plan for minimizing A single sampling plan for minimizing
inspection costs when there is a continuing inspection costs when there is a continuing
supply of lots of raw materials, component supply of lots of raw materials, component
parts, subassemblies, and finished parts parts, subassemblies, and finished parts
from the same sourcefrom the same source..

Applicable to chemical and physical Applicable to chemical and physical
characteristics that require laboratory characteristics that require laboratory
analysis.analysis.
Skip Lot SamplingSkip Lot Sampling
46

47. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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When i consecutive lots areWhen i consecutive lots are
found to be conformingfound to be conforming
Begin by inspecting every lotBegin by inspecting every lot
Discontinue inspection of every lotDiscontinue inspection of every lot
Inspect a fraction, f, of the lotsInspect a fraction, f, of the lots
In a random mannerIn a random manner
When an inspected lot is found When an inspected lot is found
nonconformingnonconforming
Procedure for SkSP-1 PlansProcedure for SkSP-1 Plans
Figure 10-7 Procedure SkSP-1 plans
47

48. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Provides procedures to reduce the
inspection effort when the supplier’s
quality is superior.
A skip-lot scheme used in conjunction
with attribute lot-by-lot plans given in
ASQ Z1.4
ANSI/ASQ S1ANSI/ASQ S1
48

49. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Requirements to use ANSI/ASQ S1
1.Have a documented system for controlling
product quality and design changes
2.Have instituted a system that is capable of
detecting and correcting changes that
might adversely affect quality.
3.Not have experienced an organizational
change that might adversely affect quality
ANSI/ASQ S1ANSI/ASQ S1
49

50. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Additional requirements of the product:
Be of stable design
Have been manufactured on a continuous
basis for at least 6 months unless agreed to a
longer period.
Have been on normal and reduced
inspection during the qualification period.
Have maintained a quality level at or less
than the AQL for at least 6 months.
ANSI/ASQ S1ANSI/ASQ S1
50

51. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Other:
The previous 10 or more consecutive lots have
been accepted
The min cumulative sample size for the last 10
or more consecutive lots have been met.
The acceptance numbers for the last 2 lots
have been met
ANSI/ASQ S1ANSI/ASQ S1
51

52. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Sampling for Continuous ProductionSampling for Continuous Production
51
Acceptance sampling for continuous
production implies that manufacturing
operations do not create lots as part of
the normal part of the production
process.
Parts are produced by a
continuous process on a conveyor
or similar system..

53. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Plans for continuous production consist of
alternating sequences of sampling
inspection and screening (100%) inspection.
Plans begin with 100% inspection and
convert to sampling after a stated number
of items are free of nonconformities.
Sampling continues until a stated number
of nonconforming units are found, at
which time 100% inspection in reinstated.
53
Sampling for Continuous ProductionSampling for Continuous Production

54. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Applicable to attribute, nondestructive
inspection of moving product.
Inspection should be easy and rapid
Process must be capable of
manufacturing homogeneous product
Sampling for Continuous ProductionSampling for Continuous Production
54

55. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Developed by Dodge
CSP-1, CSP-2, CSP-3
Later, MIL-STD-1235B
Sampling for Continuous ProductionSampling for Continuous Production
55

56. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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CSP-1
Begins with 100% inspection of the
product in the order of production
until a certain number of successive
units are free of nonconformities.
56
Sampling for Continuous ProductionSampling for Continuous Production

57. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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CSP-1
Sampling inspection is then instituted
Samples are selected in such a
manner as to minimize any bias
If a nonconformity occurs, sampling is
discontinued and 100% inspection begins..
Sampling for Continuous ProductionSampling for Continuous Production
57

58. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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The Screening Crew Inspects 100% of the Units
When i Consecutive Units Are Found Free of
Nonconformities Concerned,
The Screening Crew is Released from 100% Inspection
and the Sampling Inspector Inspects a Fraction, f, of
the Units, Where the Sample Units are Selected in a
Random Manner.
When the Sampling Inspector Finds One of the
Nonconformities Concerned,
Start
CSP-1 and CSP-F PlansCSP-1 and CSP-F Plans
58

59. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Standard is composed of five different
continuous sampling plans.
Designated by code letters
MIL-STD-1235BMIL-STD-1235B
59

60. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Inspection is by attributes for
nonconforming units using three classes of
severity:
Critical
Major
Minor
Each of the plans incorporates a provision
for discontinuance of inspection
MIL-STD-1235BMIL-STD-1235B
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61. Besterfield: Quality Control, 8
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ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Shainin Lot Plot
ANSI/ASQ Z1.9-2003
Acceptance Sampling Plans for Acceptance Sampling Plans for
VariablesVariables
61

62. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Shainin Lot Plot
Random sample of 10 subgroups of 5 each
Find average and range
Construct a histogram
Calculate Xdouble bar, R bar
Calculate ULL and LLL
Compare to lot plots in Figure 10-15
Acceptance Sampling Plans for Acceptance Sampling Plans for
VariablesVariables
62

63. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Acceptance Sampling Plans for Acceptance Sampling Plans for
VariablesVariables
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ANSI/ASQ Z1.9-2003 Sampling
Procedures and Tables for Inspection
by Variables for Percent
Nonconforming is an acceptance
sampling system to be used on a
continuing stream of lots for
Acceptance Quality Limit (AQL)
specified.

64. Besterfield: Quality Control, 8
th
ed.. © 2009 Pearson Education, Upper Saddle River, NJ 07458.
All rights reserved
Acceptance Sampling Plans for Acceptance Sampling Plans for
VariablesVariables
64
ANSI/ASQ Z1.9-2003 provides tightened,
normal, and reduced plans to be used on
measurements which are normally
distributed. Variation may be measured
by sample standard deviation, sample
range, or known standard deviation. It is
applicable only when the normality of
the measurements is assured.