ASTM E2234-2008 Standard Practice for Sampling a Stream of Product by Attributes Indexedby AQL.pdf

1、Designation: E 2234 08An American National StandardStandard Practice forSampling a Stream of Product by Attributes Indexed byAQL1This standard is issued under the fixed designation E 2234; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi

2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 PurposeThis practice establishes lot or batch sam-pling plans and procedures for inspection by attri

3、butes usingMIL-STD-105E as a basis for sampling a steady stream of lotsindexed by AQL. The tabled calculations are based on theprobabilistic theory of recurrent events when a series of lots orbatches are produced in a stable environment.1.2 ApplicationSampling plans designated in this publi-cation a

4、re applicable, but not limited, to inspection of thefollowing: (1) end items, (2) components and raw materials, (3)operations or services, (4) materials in process, (5) supplies instorage, (6) maintenance operations, (7) data or records, and(8) administrative procedures.1.2.1 These plans are intende

5、d primarily to be used for acontinuing series of lots or batches. The plans may also be usedfor the inspection of isolated lots or batches, but, in this lattercase, the user is cautioned to consult the operating character-istic curves and Table VI or Table VII to find a plan which willyield the desi

6、red protection (see 4.11).1.2.2 This practice should be used to guide the user in thedevelopment of an inspection strategy that provides a costeffective approach to attaining confidence in product compli-ance with contractual technical requirements. The user iswarned of the assumed risks relative to

7、 the chosen sample sizeand AQL.1.2.3 This practice provides the sampling plans of MIL-STD-105E in ASTM format for use by ASTM committees andothers. It recognizes the continuing usage of MIL-STD-105 inindustries supported by ASTM. The practiceprovides the fun-damental basis for many existing sampling

8、 procedures cur-rently in effect in laboratories and other facilities. As such, itprovides a primary source for other AQL standards and forspecifically engineered sampling plans developed by otherstandards bodies and individual facilities and appearing invarious forms on the shelves of countless lab

9、oratories andoperations. It replaces the AQL scheme previously incorpo-rated in the Related Materials Section of Volume 14.02 of theAnnual Book of ASTM Standards .2. Referenced Documents2.1 ASTM Standards:2E 456 Terminology Relating to Quality and StatisticsE 1994 Practice for Use of Process Oriente

10、d AOQL andLTPD Sampling Plans2.2 Other Standard:MIL-STD-105E Sampling Procedures and Tables for In-spection by Attributes33. Terminology3.1 Definitions: Terminology E 456 provides a more exten-sive list of terms in E11 standards.3.1.1 acceptance quality limit (AQL), n quality limit thatis the worst

11、tolerable process average when a continuing seriesof lots is submitted for acceptance sampling.3.1.1.1 DiscussionThis definition supersedes that given inMIL-STD-105E.3.1.1.2 DiscussionA sampling plan and an AQL arechosen in accordance with the risk assumed. Use of a value ofAQL for a certain defect

12、or group of defects indicates that thesampling plan will accept the great majority of the lots orbatches provided the process average level of percent defective(or defects per hundred units) in these lots or batches are nogreater than the designated value of AQL. Thus, the AQL is adesignated value o

13、f percent defective (or defects per hundredunits) for which lots will be accepted most of the time by thesampling procedure being used. The sampling plans providedherein are so arranged that the probability of acceptance at thedesignated AQL value depends upon the sample size, beinggenerally higher

14、for large samples than for small ones for agiven AQL. The AQL alone does not identify the chances ofaccepting or rejecting individual lots or batches but moredirectly relates to what might be expected from a series of lotsor batches, provided the steps indicated in this publication aretaken. It is n

15、ecessary to refer to the operating characteristiccurve of the plan to determine the relative risks.1This practice is under the jurisdiction of ASTM Committee E11 on Quality andStatistics and is the direct responsibility of Subcommittee E11.30 on StatisticalQuality Control.Current edition approved Oc

16、t. 1, 2008. Published October 2008. Originallyapproved in 2005. Last previous edition approved in 2005 as E 223405.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to t

17、he standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.

18、2 average outgoing quality (AOQ), n the averagepercent defective of outgoing product including all acceptedlots or batches after any defectives found in them are replacedby acceptable units, plus all lots or batches which are notaccepted after such lots or batches have been effectively 100 %inspecte

19、d and all defective units replaced by acceptable units.E 19943.1.3 average outgoing quality limit (AOQL), nthe maxi-mum AOQ for a given acceptance sampling plan for allpossible incoming percentages defective for the process.E 19943.1.3.1 DiscussionFactors for computing AOQL valuesare given in Table

20、V-Afor each of the single sampling plans fornormal inspection and in Table V-B for each of the singlesampling plans for tightened inspection.3.1.4 batch (in inspection), na collection of units ofproduct produced under conditions that are considered uniformand from which a sample is drawn and inspect

21、ed, and maydiffer from a collection of units designated as a batch for otherpurposes, for example, production, shipment, etc.3.1.5 batch size, nthe number of units of product in abatch.3.1.6 classification of defects, nthe enumeration of pos-sible defects of the unit of product arranged according to

22、 theirseriousness, that is, critical, major, or minor defect.3.1.7 critical defect, na defect that judgment and experi-ence indicate would result in hazardous or unsafe conditionsfor individuals using, maintaining, or depending upon theproduct, or a defect that judgment and experience indicate islik

23、ely to prevent performance of the function of a major enditem.3.1.8 critical defective, na unit of product which containsone or more critical defects and may also contain major and/orminor defects.3.1.9 defect, nany nonconformance of the unit of productwith specified requirements.3.1.10 defective, n

24、a unit of product which contains one ormore defects.3.1.11 defects per hundred units, nany given quantity ofunits of product is one hundred times the number of defectscontained therein (one or more defects being possible in anyunit of product) divided by the total number of units of product,that is:

25、Defects per hundred units 5Number of defects 3100Number of units inspected(1)3.1.12 inspection, nthe process of measuring, examining,testing, or otherwise comparing the unit of product with therequirements.3.1.13 inspection by attributes, ninspection whereby ei-ther the unit of product is classified

26、 simply as defective ornon-defective, or the number of defects in the unit of productis counted, with respect to a given requirement or set ofrequirements.3.1.14 lot, nsee batch.3.1.15 lot size, nsee batch size.3.1.16 major defect, na defect, other than critical, that islikely to result in failure,

27、or to reduce materially the usabilityof the unit of product for its intended purpose.3.1.17 major defective, na unit of product which containsone or more major defects, and may also contain minor defectsbut contains no critical defect.3.1.18 minor defect, na defect that is not likely to reducemateri

28、ally the usability of the unit of product for its intendedpurpose, or is a departure from established standards havinglittle bearing on the effective use or operation of the unit.3.1.19 minor defective, na unit of product which containsone or more minor defects but contains no critical or majordefec

29、t.3.1.20 percent defective, nany given quantity of units ofproduct one hundred times the number of defective units ofproduct contained therein divided by the total number of unitsof product, that is:Percent Defective 5Number of defectives 3 100Number of units inspected(2)3.1.21 process average (in i

30、nspection), n the averagepercent defective or average number of defects per hundredunits (whichever is applicable) of product submitted by thesupplier for original inspection.3.1.21.1 DiscussionOriginal inspection is the first inspec-tion of a particular quantity of product as distinguished fromthe

31、inspection of product which has been resubmitted afterprior rejection.3.1.22 sample, na group of items, observations, testresults, or portions of material, taken from a large collection ofitems, observations, test results, or quantities of material,which serves to provide information that may be use

32、d as a basisfor making a decision concerning the larger collection.3.1.22.1 DiscussionA sample consists of one or moreunits of product drawn from a lot or batch, the units of thesample being selected at random without regard to theirquality. The number of units of product in the sample is thesample

33、size. E 22343.1.23 sample size code letter, na device used along withthe AQL for locating a sampling plan on a table of samplingplans.3.1.24 sampling plan (in inspection), n a plan that indi-cates the number of units of product from each lot or batchwhich are to be inspected (sample size or series o

34、f samplesizes) and the criteria for determining the acceptability of thelot or batch (acceptance and rejection numbers).3.1.25 unit of product, nthat which is inspected in order todetermine its classification as defective or non-defective or tocount the number of defects.3.1.25.1 Discussion It may b

35、e a single article, a pair, a set,a length, an area, an operation, a volume, a component of anend product, or the end product itself. The unit of product mayor may not be the same as the unit of purchase, supply,production, or shipment.4. Significance and Use4.1 Written ProceduresWritten procedures

36、are ordinarilydeveloped and made available for the customers review, uponrequest. When the written procedures indicate use of thisstandard, they shall comply with the requirements of thispracticeand reference appropriate parts as necessary.E22340824.2 NonconformanceThe extent of nonconformance ofpro

37、duct shall be expressed either in terms of percent defectiveor in terms of defects per hundred units.4.3 Formation and Identification of Lots or Batches Theproduct shall be assembled into identifiable lots, sublots,batches, or in such other manner as may be prescribed. Each lotor batch shall, as far

38、 as is practicable, consist of units ofproduct of a single type, grade, class, size, and composition,manufactured under essentially the same conditions, and atessentially the same time. The lots or batches shall be identifiedby the contractor and shall be kept intact in adequate andsuitable storage

39、space.4.4 AQL:4.4.1 AQL UseThe AQL, together with the Sample SizeCode Letter, is used for indexing the sampling plans providedherein.4.4.2 LimitationThe selection or use of an AQL shall notimply that the contractor has the right to supply any defectiveunit of product.4.4.3 Choosing AQLsDifferent AQL

40、s may be chosen forgroups of defects considered collectively, or for individualdefects. An AQL for a group of defects may be chosen inaddition to AQLs for individual defects, or subgroups, withinthat group. AQL values of 10.0 or less may be expressed eitherin percent defective or in defects per hund

41、red units; those over10.0 shall be expressed in defects per hundred units only.4.5 Sampling:4.5.1 Representative (Stratified) SamplingWhen appro-priate, the number of units in the sample shall be selected inproportion to the size of sublots or sub-batches, or parts of thelot or batch, identified by

42、some rational criterion. Whenrepresentative sampling is used, the units from each sublot,sub-batch or part of the lot or batch shall be selected at random.4.5.2 Time of SamplingA sample may be drawn after allthe units comprising the lot or batch have been assembled, orsample units may be drawn durin

43、g assembly of the lot or batch,in which case the size of the lot or batch will be determinedbefore any sample units are drawn. If the sample units aredrawn during assembly of the lot or batch, and if the rejectionnumber is reached before the lot is completed, that portion ofthe lot already completed

44、 shall be rejected. The cause of thedefective product shall be determined and corrective actiontaken, after which a new lot or batch shall be begun.4.5.3 Double or Multiple SamplingWhen double or mul-tiple sampling is to be used, each sample shall be selected overthe entire lot or batch.4.6 Inspecti

45、on ProceduresNormal inspection will be usedat the start of inspection. Normal, tightened or reducedinspection shall continue unchanged for each class of defects ordefectives on successive lots or batches except where theswitching procedures given below require change. The switch-ing procedures shall

46、 be applied to each class of defects ordefectives independently.4.7 Switching Procedures:4.7.1 Normal to TightenedWhen normal inspection is ineffect, tightened inspection shall be instituted when 2 out of 2,3, 4, or 5 consecutive lots or batches have been rejected onoriginal inspection (that is, ign

47、oring resubmitted lots or batchesfor this procedure).4.7.2 Tightened to NormalWhen tightened inspection isin effect, normal inspection shall be instituted when 5 consecu-tive lots or batches have been considered acceptable on originalinspection.4.7.3 Normal to ReducedWhen normal inspection is ineffe

48、ct, reduced inspection shall be instituted provided that all ofthe following conditions are satisfied:4.7.3.1 The preceding 10 lots or batches (or more, asindicated by the note to Table VIII) have been on normalinspection and all have been accepted on original inspection;and4.7.3.2 The total number

49、of defectives (or defects) in thesamples from the preceding 10 lots or batches (or such othernumber as was used for condition 4.7.3.1 above) is equal to orless than the applicable number given in Table VIII. If doubleor multiple sampling is in use, all samples inspected should beincluded, not “first” samples only; and4.7.3.3 Production is at a steady rate; and4.7.3.4 Reduced inspection is considered desirable.4.7.4 Reduced to NormalWhen reduced inspection is ineffect, normal inspection shall be instituted if any of thefollowing occur on