ASTM_E_105_-_10.pdf

Designation:E10510An American National StandardStandard Practice forProbability Sampling of Materials1This standard is issued under the fixed designation E105;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 is primarily a statement of principles forthe guidance of ASTM technical committees and others in thepreparation of a sampling plan for a specific material.2.Referenced Documents2.1 ASTM Standards:E122 Practice for Calculating Sample Size to Estimate,WithSpecified Precision,the Average for a Characteristic of aLot or ProcessE141 Practice for Acceptance of Evidence Based on theResults of Probability SamplingE456 Terminology Relating to Quality and StatisticsE1402 Guide for Sampling Design3.Terminology3.1 Definitions:3.1.1 For general terminology,refer to Terminology E456and Guide E1402.3.1.2 judgment sampling,na procedure whereby enu-merators select a few items of the population,based on visual,positional,or other cues that are believed to be related to thevariable of interest,so that the selected items appear to matchthe population.3.1.3 probability sampling plan,na sampling plan whichmakes use of the theory of probability to combine a suitableprocedure for selecting sample items with an appropriateprocedure for summarizing the test results so that inferencesmay be drawn and risks calculated from the test results by thetheory of probability.3.1.3.1 DiscussionFor any given set of conditions,therewill usually be several possible plans,all valid,but differing inspeed,simplicity,and cost.Further discussion is provided inPractice E141.4.Significance and Use4.1 The purpose of the sample may be to estimate propertiesof a larger population,such as a lot,pile or shipment,thepercentage of some constituent,the fraction of the items thatfail to meet(or meet)a specified requirement,the averagecharacteristic or quality of an item,the total weight of theshipment,or the probable maximum or minimum content of,say,some chemical.4.2 The purpose may be the rational disposition of a lot orshipment without the intermediate step of the formation of anestimate.4.3 The purpose may be to provide aid toward rationalaction concerning the production process that generated the lot,pile or shipment.4.4 Whatever the purpose of the sample,adhering to theprinciples of probability sampling will allow the uncertainties,such as bias and variance of estimates or the risks of therational disposition or action,to be calculated objectively andvalidly from the theory of combinatorial probabilities.Thisassumes,of course,that the sampling operations themselveswere carried out properly,as well.For example,that anyrandom numbers required were generated properly,the units tobe sampled from were correctly identified,located,and drawn,and the measurements were made with measurement error at alevel not exceeding the required purposes.4.5 Determination of bias and variance and of risks can becalculated when the selection was only partially determined byrandom numbers and a frame,but they then require supposi-tions and assumptions which may be more or less mistaken orrequire additional data which may introduce experimentalerror.5.Characteristics of a Probability Sampling Plan5.1 A probability sampling plan will possess certain char-acteristics of importance,as follows:5.1.1 It will possess an objective procedure for the selectionof the sample,with the use of random numbers.5.1.2 It will include a definite formula for the estimate,ifthere is to be an estimate;also for the standard error of anyestimate.If the sample is used for decision without theintermediate step of an estimate,the decision process willfollow definite rules.In acceptance sampling,for example,these are often based on predetermined risks of taking theundesired action when the true levels of the characteristicconcerned have predetermined values;for example,acceptableand rejectable quality levels may be specified.1This practice is under the jurisdiction ofASTM Committee E11 on Quality andStatistics and is the direct responsibility of Subcommittee E11.10 on Sampling/Statistics.Current edition approved Oct.1,2010.Published November 2010.Originallyapproved in 1954.Last previous edition approved in 2004 as E105 04.DOI:10.1520/E0105-10.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.2 The minimum requirements that must be met in order toobtain the characteristics mentioned in 5.1 appear in Section 6,which also indicates the minimum requirements for the de-scription of a satisfactory sampling plan.6.Minimum Standards for a Probability Sampling Plan6.1 For a sampling plan to have the requirements mentionedin Section 5 it is necessary:6.1.1 That every part of the pile,lot,