ASTM E2234-05
(Practice)Standard Practice for Sampling a Stream of Product by Attributes Indexedby AQL
Standard Practice for Sampling a Stream of Product by Attributes Indexedby AQL
SCOPE
1.1 PurposeThis standard establishes lot or batch sampling plans and procedures for inspection by attributes using MIL-STD-105E as a basis for sampling a steady stream of lots indexed by AQL. The tabled calculations are based on the probabilistic theory of recurrent events when a series of lots or batches are produced in a stable environment.
1.2 ApplicationSampling plans designated in this publication are applicable, but not limited, to inspection of the following: (1) end items, (2) components and raw materials, (3) operations or services, (4) materials in process, (5) supplies in storage, (6) maintenance operations, (7) data or records, and (8) administrative procedures.
1.2.1 These plans are intended primarily to be used for a continuing series of lots or batches. The plans may also be used for the inspection of isolated lots or batches, but, in this latter case, the user is cautioned to consult the operating characteristic curves and Table VI or Table VII to find a plan which will yield the desired protection (see 4.11).
1.2.2 This publication should be used to guide the user in the development of an inspection strategy that provides a cost effective approach to attaining confidence in product compliance with contractual technical requirements. The user is warned of the assumed risks relative to the chosen sample size and AQL.
1.2.3 This standard provides the sampling plans of MIL-STD-105E in ASTM format for use by ASTM committees and others. It recognizes the continuing usage of MIL-STD-105 in industries supported by ASTM. The standard provides the fundamental basis for many existing sampling procedures currently in effect in laboratories and other facilities. As such, it provides a primary source for other AQL standards and for specifically engineered sampling plans developed by other standards bodies and individual facilities and appearing in various forms on the shelves of countless laboratories and operations. It replaces the AQL scheme previously incorporated in the Related Materials Section of Volume 14.02 of the Annual Book of ASTM Standards.
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An American National Standard
Designation:E2234–05
Standard Practice for
Sampling a Stream of Product by Attributes Indexed by
AQL
This standard is issued under the fixed designation E 2234; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope rated in the Related Materials Section of Volume 14.02 of the
Annual Book of ASTM Standards.
1.1 Purpose—This standard establishes lot or batch sam-
pling plans and procedures for inspection by attributes using
2. Referenced Documents
MIL-STD-105E as a basis for sampling a steady stream of lots
2.1 ASTM Standards:
indexed by AQL. The tabled calculations are based on the
E 456 Terminology Relating to Quality and Statistics
probabilistic theory of recurrent events when a series of lots or
E 1994 Practice for Use of Process Oriented AOQL and
batches are produced in a stable environment.
LTPD Sampling Plans
1.2 Application—Sampling plans designated in this publi-
cation are applicable, but not limited, to inspection of the
3. Terminology
following:(1)enditems,(2)componentsandrawmaterials,(3)
3.1 Definitions:
operations or services, (4) materials in process, (5) supplies in
3.1.1 acceptance quality limit (AQL), n—quality limit that
storage, (6) maintenance operations, (7) data or records, and
is the worst tolerable process average when a continuing series
(8) administrative procedures.
of lots is submitted for acceptance sampling.
1.2.1 These plans are intended primarily to be used for a
3.1.1.1 Discussion—Thisdefinitionsupercedesthatgivenin
continuingseriesoflotsorbatches.Theplansmayalsobeused
MIL-STD-105E.
for the inspection of isolated lots or batches, but, in this latter
3.1.1.2 Discussion—A sampling plan and an AQL are
case, the user is cautioned to consult the operating character-
chosen in accordance with the risk assumed. Use of a value of
istic curves andTableVI orTableVII to find a plan which will
AQL for a certain defect or group of defects indicates that the
yield the desired protection (see 4.11).
sampling plan will accept the great majority of the lots or
1.2.2 This publication should be used to guide the user in
batches provided the process average level of percent defective
the development of an inspection strategy that provides a cost
(or defects per hundred units) in these lots or batches are no
effective approach to attaining confidence in product compli-
greater than the designated value of AQL. Thus, the AQL is a
ance with contractual technical requirements. The user is
designated value of percent defective (or defects per hundred
warned of the assumed risks relative to the chosen sample size
units) for which lots will be accepted most of the time by the
and AQL.
sampling procedure being used. The sampling plans provided
1.2.3 This standard provides the sampling plans of MIL-
herein are so arranged that the probability of acceptance at the
STD-105E inASTM format for use byASTM committees and
designated AQL value depends upon the sample size, being
others. It recognizes the continuing usage of MIL-STD-105 in
generally higher for large samples than for small ones for a
industries supported by ASTM. The standard provides the
given AQL. The AQL alone does not identify the chances of
fundamental basis for many existing sampling procedures
accepting or rejecting individual lots or batches but more
currently in effect in laboratories and other facilities. As such,
directly relates to what might be expected from a series of lots
it provides a primary source for other AQL standards and for
or batches, provided the steps indicated in this publication are
specifically engineered sampling plans developed by other
taken. It is necessary to refer to the operating characteristic
standards bodies and individual facilities and appearing in
curve of the plan to determine the relative risks.
various forms on the shelves of countless laboratories and
operations. It replaces the AQL scheme previously incorpo-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This practice is under the jurisdiction ofASTM Committee E11 on Quality and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Statistics and is the direct responsibility of Subcommittee E11.30 on DataAnalysis. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2005. Published January 2006. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2234–05
3.1.2 average outgoing quality (AOQ), n—the average per- 3.1.17 major defective, n—a unit of product which contains
cent defective of outgoing product including all accepted lots one or more major defects, and may also contain minor defects
or batches after any defectives found in them are replaced by but contains no critical defect.
acceptableunits,plusalllotsorbatcheswhicharenotaccepted
3.1.18 minor defect, n—a defect that is not likely to reduce
after such lots or batches have been effectively 100 % in-
materially the usability of the unit of product for its intended
spected and all defective units replaced by acceptable units.
purpose, or is a departure from established standards having
E 1994
little bearing on the effective use or operation of the unit.
3.1.3 average outgoing quality limit (AOQL), n—the maxi-
3.1.19 minor defective, n—a unit of product which contains
mum AOQ for a given acceptance sampling plan for all
one or more minor defects but contains no critical or major
possible incoming percentages defective for the process.
defect.
E 1994
3.1.20 percent defective, n—any given quantity of units of
3.1.3.1 Discussion—Factors for computing AOQL values
product one hundred times the number of defective units of
aregiveninTableV-Aforeachofthesinglesamplingplansfor
product contained therein divided by the total number of units
normal inspection and in Table V-B for each of the single
of product, that is:
sampling plans for tightened inspection.
Number of defectives 3 100
3.1.4 batch (in inspection), n—a collection of units of Percent Defective 5 (2)
Number of units inspected
product produced under conditions that are considered uniform
3.1.21 process average (in inspection), n—the average per-
and from which a sample is drawn and inspected, and may
cent defective or average number of defects per hundred units
differ from a collection of units designated as a batch for other
(whichever is applicable) of product submitted by the supplier
purposes, for example, production, shipment, etc.
for original inspection.
3.1.5 batch size, n—the number of units of product in a
3.1.21.1 Discussion—Original inspection is the first inspec-
batch.
tion of a particular quantity of product as distinguished from
3.1.6 classification of defects, n—the enumeration of pos-
the inspection of product which has been resubmitted after
sible defects of the unit of product arranged according to their
prior rejection.
seriousness, that is, critical, major, or minor defect.
3.1.22 sample, n—a group of items, observations, test
3.1.7 critical defect, n—a defect that judgment and experi-
results, or portions of material, taken from a large collection of
ence indicate would result in hazardous or unsafe conditions
items, observations, test results, or quantities of material,
for individuals using, maintaining, or depending upon the
whichservestoprovideinformationthatmaybeusedasabasis
product, or a defect that judgment and experience indicate is
for making a decision concerning the larger collection.
likely to prevent performance of the function of a major end
item. 3.1.22.1 Discussion—A sample consists of one or more
units of product drawn from a lot or batch, the units of the
3.1.8 critical defective, n—a unit of product which contains
one or more critical defects and may also contain major and/or sample being selected at random without regard to their
minor defects. quality. The number of units of product in the sample is the
3.1.9 defect, n—any nonconformance of the unit of product sample size. E 2234
with specified requirements. 3.1.23 sample size code letter, n—a device used along with
3.1.10 defective, n—a unit of product which contains one or the AQL for locating a sampling plan on a table of sampling
more defects. plans.
3.1.11 defects per hundred units, n—any given quantity of
3.1.24 sampling plan (in inspection), n—a plan that indi-
units of product is one hundred times the number of defects
cates the number of units of product from each lot or batch
contained therein (one or more defects being possible in any
which are to be inspected (sample size or series of sample
unitofproduct)dividedbythetotalnumberofunitsofproduct,
sizes) and the criteria for determining the acceptability of the
that is:
lot or batch (acceptance and rejection numbers).
3.1.25 unitofproduct,n—thatwhichisinspectedinorderto
Number of defects 3100
Defects per hundred units 5 (1)
determine its classification as defective or non-defective or to
Number of units inspected
count the number of defects. It may be a single article, a pair,
3.1.12 inspection, n—the process of measuring, examining,
a set, a length, an area, an operation, a volume, a component of
testing, or otherwise comparing the unit of product with the
an end product, or the end product itself.
requirements.
3.1.25.1 Discussion— The unit of product may or may not
3.1.13 inspection by attributes, n—inspection whereby ei-
be the same as the unit of purchase, supply, production, or
ther the unit of product is classified simply as defective or
shipment.
non-defective, or the number of defects in the unit of product
is counted, with respect to a given requirement or set of
4. Significance and Use
requirements.
3.1.14 lot, n—see batch. 4.1 Written Procedures—Written procedures are ordinarily
3.1.15 lot size, n—see batch size.
developed and made available for the customer’s review, upon
3.1.16 major defect, n—a defect, other than critical, that is request. When the written procedures indicate use of this
likely to result in failure, or to reduce materially the usability standard, they shall comply with the requirements of this
of the unit of product for its intended purpose. standard and reference appropriate parts as necessary.
E2234–05
4.2 Nonconformance—The extent of nonconformance of 3, 4, or 5 consecutive lots or batches have been rejected on
product shall be expressed either in terms of percent defective originalinspection(thatis,ignoringresubmittedlotsorbatches
or in terms of defects per hundred units. for this procedure).
4.3 Formation and Identification of Lots or Batches—The 4.7.2 Tightened to Normal—When tightened inspection is
product shall be assembled into identifiable lots, sublots,
in effect, normal inspection shall be instituted when 5 consecu-
batches,orinsuchothermannerasmaybeprescribed.Eachlot tivelotsorbatcheshavebeenconsideredacceptableonoriginal
or batch shall, as far as is practicable, consist of units of
inspection.
product of a single type, grade, class, size, and composition,
4.7.3 Normal to Reduced—When normal inspection is in
manufactured under essentially the same conditions, and at
effect,reducedinspectionshallbeinstitutedprovidedthatallof
essentiallythesametime.Thelotsorbatchesshallbeidentified
the following conditions are satisfied:
by the contractor and shall be kept intact in adequate and
4.7.3.1 The preceding 10 lots or batches (or more, as
suitable storage space.
indicated by the note to Table VIII) have been on normal
4.4 AQL:
inspection and all have been accepted on original inspection;
4.4.1 AQL Use—The AQL, together with the Sample Size
and
Code Letter, is used for indexing the sampling plans provided
4.7.3.2 The total number of defectives (or defects) in the
herein.
samples from the preceding 10 lots or batches (or such other
4.4.2 Limitation—The selection or use of an AQL shall not
number as was used for condition 4.7.3.1 above) is equal to or
imply that the contractor has the right to supply any defective
less than the applicable number given in Table VIII. If double
unit of product.
or multiple sampling is in use, all samples inspected should be
4.4.3 Choosing AQLs—Different AQLs may be chosen for
included, not “first” samples only; and
groups of defects considered collectively, or for individual
4.7.3.3 Production is at a steady rate; and
defects. An AQL for a group of defects may be chosen in
4.7.3.4 Reduced inspection is considered desirable.
addition to AQLs for individual defects, or subgroups, within
4.7.4 Reduced to Normal—When reduced inspection is in
that group.AQLvalues of 10.0 or less may be expressed either
effect, normal inspection shall be instituted if any of the
in percent defective or in defects per hundred units; those over
following occur on original inspection:
10.0 shall be expressed in defects per hundred units only.
4.7.4.1 A lot or batch is rejected; or
4.5 Sampling:
4.7.4.2 A lot or batch is considered acceptable under the
4.5.1 Representative (Stratified) Sampling—When appro-
procedures of 4.10.1.4,or
priate, the number of units in the sample shall be selected in
4.7.4.3 Production becomes irregular or delayed; or
proportion to the size of sublots or sub-batches, or parts of the
4.7.4.4 Other conditions warrant that normal inspection
lot or batch, identified by some rational criterion. When
shall be instituted.
representative sampling is used, the units from each sublot,
4.8 Discontinuation of Inspection. If the cumulative number
sub-batchorpartofthelotorbatchshallbeselectedatrandom.
of lots not accepted in a sequence of consecutive lots on
4.5.2 Time of Sampling—A sample may be drawn after all
original tightened inspection reaches five, the acceptance
the units comprising the lot or batch have been assembled, or
procedures of this standard shall be discontinued. Inspection
sampleunitsmaybedrawnduringassemblyofthelotorbatch,
under the provisions of this standard shall not be resumed until
in which case the size of the lot or batch will be determined
corrective action has been taken. Tightened inspection shall
before any sample units are drawn. If the sample units are
then be used as if 4.7.1 had been invoked.
drawn during assembly of the lot or batch, and if the rejection
4.9 Sampling Plans:
number is reached before the lot is completed, that portion of
4.9.1 Inspection Level—Theinspectionleveldeterminesthe
the lot already completed shall be rejected. The cause of the
relationship between the l
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