ASTM_E_2696_-_09_2013.pdf

Designation:E269609(Reapproved 2013)An American National StandardStandard Practice forLife and Reliability Testing Based on the ExponentialDistribution1This standard is issued under the fixed designation E2696;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 standard sampling procedures andtables for life and reliability testing in procurement,supply,andmaintenance quality control operations as well as in researchand development activities.1.2 This practice describes general procedures and defini-tions of terms used in life test sampling and describes specificprocedures and applications of the life test sampling plans fordetermining conformance to established reliability require-ments.1.3 This practice is an adaptation of the Quality Control andReliability Handbook H-108,“Sampling Procedures andTables for Life and Reliability Testing(Based on ExponentialDistribution),”U.S.Government Printing Office,April 29,1960.1.4 A system of units is not specified in this practice.1.5 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 AQLE2555 Practice for Factors and Procedures for Applying theMIL-STD-105 Plans in Life and Reliability Inspection3.Terminology3.1 Definitions:3.1.1 See Terminology E456 for a more extensive listing ofterms in ASTM Committee E11 standards.3.1.2 consumers risk,nprobability that a lot havingspecified rejectable quality level will be accepted under adefined sampling plan.E25553.1.2.1 DiscussionIn this practice,the consumers risk isthe probability of accepting lots with mean time to failure 1.3.1.2.2 DiscussionFor the procedures of 9.7 and 9.8,theconsumers risk may also be defined as the probability ofaccepting lots with unacceptable proportion of lot failingbefore specified time,p1.3.1.3 life test,nprocess of placing one or more units ofproduct under a specified set of test conditions and measuringthe time until failure for each unit.3.1.4 mean time to failure,n in life testing,the averagelength of life of items in a lot.3.1.4.1 DiscussionAlso known as mean life.3.1.5 number of failures,nnumber of failures that haveoccurred at the time the decision as to lot acceptability isreached.3.1.5.1 DiscussionThe expected number of failures re-quired for decision is the average of the number of failuresrequired for decision when life tests are conducted on a largenumber of samples drawn at random from the same exponen-tial distribution.3.1.6 producers risk,nprobability that a lot havingspecified acceptable quality level will be rejected under adefined sampling plan.3.1.6.1 DiscussionIn this practice,the producers risk isthe probability of rejecting lots with mean time to failure 0.3.1.6.2 DiscussionFor the procedures of 9.7 and 9.8,theproducers risk may also be defined as the probability ofrejecting lots with acceptable proportion of lot failing beforespecified time,p0.3.1.7 sequential life test,nlife test sampling plan wherebyneither the number of failures nor the time required to reach adecision are fixed in advance but instead decisions depend onthe accumulated results of the life test.3.1.8 unit of product,nthat which is inspected to deter-mine its classification as defective or nondefective or to countthe number of defects.E22341This 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 April 1,2013.Published April 2013.Originallyapproved in 2009.Last previous edition approved in 2009 as E2696 091.DOI:10.1520/E2696-09R13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.9 waiting time,nin life testing,the time elapsed fromthe start of testing until a decision is reached as to lotacceptability.3.1.9.1 DiscussionThe expected waiting time required fordecision is the average of the waiting times required fordecision when life tests are conducted on a large number ofsamples drawn at random from the same exponential distribu-tion.4.Significance and Use4.1 This practice was prepared to meet a growing need forthe use of