Co-operating organizations
Foreword
Guide
1 Introduction
2 The aim of the sampling method
3 The words 'lot' and 'batch'
4 Unit of product
5 Inspection by attributes
6 Presentation of product
7 Description of specification
8 Drawing a sampling plan from the tables
9 Defects and defectives
10 Single sampling
11 Meaning of acceptable quality level
12 Preferred AQLs
13 Meaning of inspection level
14 The sample sizes
15 Operating characteristic curves
16 Batches
17 Normal inspection
18 Tightened inspection
19 Switching rules
20 Methods for reducing the risks
21 Reduced inspection
22 Concessions
23 Defect classification
24 Critical defects
25 Double sampling
16 Multiple sampling
27 Sequential sampling
28 Comparison of single, double, multiple and
sequential sampling
29 Curtailment of inspection
30 Disposal of rejected product
31 Drawing of samples
32 Supplementary information
33 Process average
34 Average outgoing quality, and its limit
35 Average sample size
36 Limiting quality and the isolated batch
37 Relation between AQL and tolerances
38 Setting an AQL
39 Setting an inspection level
40 Non-preferred AQLs
41 Preparing a specification
42 Nomograms
43 Other statistical methods
Tables
1 Relationship between sample size and batch size for
the three general inspection levels
2 Percentage of batches expected to be accepted if
quality is equal to the AQL
3 Twenty-five batches from a hypothetical inspection
process. AQL = 1.5 % defective
4 Fifteen batches from a hypothetical inspection
process. AQL = 10 % defective
5 Ten batches from a hypothetical inspection process.
AQL = 10 % defective
6 Twenty batches from a hypothetical inspection
process. Inspection level III
7 Random sampling numbers
8 AQL normal tolerance factors
Figures
1 Operating characteristic curve of a single-sampling
plan
2 The effect of a single-sampling plan
3 The ideal, but unattainable, O.C. curve
4 O.C. curve of a sampling plan designed to give a
high probability of rejection if any batch having a
quality worse than the AQL is submitted
5 O.C. curve of a sampling plan designed to give a
high probability of acceptance if any batch having a
quality better than the AQL is submitted
6 O.C. curves for two 'normal inspection' sampling
plans for AQL 1.0 % defective
7 Four sampling plans for AQL 1.5 % defective, normal
inspection, single sampling
8 Comparison of O.C. curves for single, double,
multiple and sequential sampling for AQL 4 %
defective, code letter H, normal inspection
9 Comparison of average sample sizes for single,
double, multiple and sequential sampling for AQL 4 %
defective, code letter H, normal inspection
10 Simultaneous change of AQL and tolerances when
quality is equal to the AQL
11 Comparison of O.C. curves for determining inspection
level. AQL 1 % defective, normal inspection
12 Nomogram for type of sampling, code letter and
sample size in BS 6001
13 Nomogram for AQL, sample size and acceptance
number in BS 6001