ASTM_D_6842_-_02e1.pdf

Designation:D 6842 02e1Standard Guide forDesigning Cost-Effective Sampling and Measurement Plansby Use of Estimated Uncertainty and Its Components inWaste Management Decision-Making1This standard is issued under the fixed designation D 6842;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(e)indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made in June 2003.1.Scope1.1 Waste management decisions generally involve uncer-tainty because of the fact that decisions are based on the use ofsample data.When uncertainty can be reduced or controlled,abetter decision can be achieved.One way to reduce or controluncertainty is through the estimation and control of thecomponents contributing to the overall uncertainty(or vari-ance).Control of the sizes of these variance components is anoptimization process.The optimizations results can be used toeither improve an existing sampling and analysis plan(if itshould be found to be inadequate for decision-making pur-poses)or to optimize a new plan by directing resources towhere the overall variance can be reduced the most.1.2 Estimation of the variance components from the totalvariance starts with the sampling and measurement process.The process involves two different kinds of uncertainties:random and systematic.The former is associated with impre-cision of the data,while the latter is associated with bias of thedata.This guide will discuss only sources of uncertainty of arandom nature.1.3 There may be many sources of uncertainty in wastemanagement decisions.However,this guide does not intend toaddress the issue of how these sources are identified.It is theresponsibility of the stakeholders and their technical staff toanalyze the sampling and measurement processes in order toidentify the potentially significant sources of uncertainty.Afteridentifying these sources,this guide will provide guidance onhow to collect and analyze data to obtain an estimate of thetotal uncertainty and its components.2.Terminology2.1 analysis of variance(ANOVA),na statistical methodof decomposing(or breaking down)the total variance andestimating or testing its contributing component variances forstatistical significance.2.2 balanced design,na statistical study where replicationin each of the levels of ANOVA is identical.2.3 measurement process,nthe method and procedure ofobtaining and measuring samples or their subsamples toproduce sample data.2.4 sampling process,nthe method and procedure ofcollecting physical samples from a defined population.2.5 unbalanced design,na statistical study where replica-tion in some or all of the levels of ANOVA is not identical.3.Significance and Use3.1 This guide will evaluate sample data that contain a highlevel of uncertainty for decision-making purposes and,where itis feasible,design a statistical study to estimate and reduce thesources of uncertainty.Oftentimes,historical data may beavailable and adequate for this purpose and no new study isneeded.3.1.1 This approach will help the stakeholders better under-stand where the greatest sources of uncertainty are in thesampling and analysis process.Resources can be directed towhere they can most reduce the overall uncertainty.3.1.2 Sampling and analysis design under this approach canoften be cost-efficient because(a)the reduction in uncertaintycan be done by statistical means alone and(b)the reduction canbe translated into a lower number of analyses.3.2 This guide is limited to the situation where a decision isbased on the mean of a population.It will only includediscussions of a balanced design for the collection and analysisof sample data in order to estimate the sources of uncertainty.References to unbalanced designs are provided where appro-priate.4.Uncertainty in Decision-Making4.1 Decision-Making Based on Data:4.1.1 When waste management decision-making is based ondata and when the data come from a subset of a population,thedata can be used to calculate quantities such as mean,median,1This guide is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the direct responsibility of Subcommittee D34.01 on Samplingand Monitoring.Current edition approved Dec.10,2002.Published February 2003.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.or percentage for the purpose of estimating the true value ofthese quantities in the population.These estimates can be usedto make conclusions or decisions about the population onissues such as:(1)Is the average concentration of a contami-nant at a certain site higher or lower than a regulatory standard?(2)Has the cleanup standard been met?4.1.2 However,these estimates involve uncertainty becauseof uncertainties in the sampling and measurement processes.The total uncertainty associated with an