ASTM_E_2555_-_07_2012.pdf

Designation:E255507(Reapproved 2012)An American National StandardStandard Practice forFactors and Procedures for Applying the MIL-STD-105 Plansin Life and Reliability Inspection1This standard is issued under the fixed designation E2555;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,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 This practice presents a procedure and related tables offactors for adapting Practice E2234(equivalent to MIL-STD-105)sampling plans to acceptance sampling inspection whenthe item quality of interest is life length or reliability.Factorsare provided for three alternative criteria for lot evaluation:mean life,hazard rate,and reliable life.Inspection of thesample is by attributes with testing truncated at the end of someprearranged period of time.The Weibull distribution,togetherwith the exponential distribution as a special case,is used asthe underlying statistical model.1.2 A system of units is not specified by this practice.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E456 Terminology Relating to Quality and StatisticsE2234 Practice for Sampling a Stream of Product by Attri-butes Indexed by AQL2.2 Other Documents:MIL-STD-105E Sampling Procedures and Tables for In-spection by Attributes33.Terminology3.1 Definitions:3.1.1 The terminology defined in Terminology E456 appliesto this practice unless modified herein.3.1.2 acceptance quality level(AQL),nquality limit that isthe worst tolerable process average when a continuing series oflots is submitted for acceptance sampling.E22343.1.2.1 DiscussionThis term is often referred to as the“acceptance quality limit.”3.1.2.2 DiscussionThis definition supersedes that given inMIL-STD-105E.3.1.2.3 DiscussionA sampling plan and an AQL are cho-sen in accordance with the risk assumed.Use of a value ofAQL for a certain defect 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 of 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 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 refer to theoperating characteristic curve of the plan to determine therelative risks.3.1.3 consumers risk,nprobability that a lot havingspecified rejectable quality level will be accepted under adefined sampling plan.3.1.4 double sampling plan,na multiple sampling plan inwhich up to two samplings can be taken and evaluated toaccept or reject a lot.3.1.5 limiting quality level(LQL),nquality level having aspecified consumers risk for a given sampling plan.3.1.6 lot,na definite quantity of a product or materialaccumulated under conditions that are considered uniform forsampling purposes.3.1.6.1 DiscussionThe lot for sampling may differ from acollection of units designated as a batch for other purposes,forexample,production,shipment,and so forth.1This practice is under the jurisdiction ofASTM Committee E11 on Quality andStatistics and is the direct responsibility of Subcommittee E11.30 on StatisticalQuality Control.Current edition approved May 1,2012.Published May 2012.Originallyapproved in 2007.Last previous version approved in 2007 as E2555 07.DOI:10.1520/E2555-07R12.2For 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 the standards Document Summary page onthe ASTM website.3MIL-STD-105E is also commonly referred to as“MIL-STD-105.”It is virtuallyidentical in content to its predecessor,MIL-STD-105D.These documents are out ofprint.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.7 multiple sampling plan,na sampling plan in whichsuccessive samples from a lot are drawn and after each sampleis inspected a decision is made to accept the lot,reject the lot,or to take another sample,based on quality level of thecombined samples