ASTM_G_169_-_01_2013.pdf

Designation:G16901(Reapproved 2013)Standard Guide forApplication of Basic Statistical Methods to WeatheringTests1This standard is issued under the fixed designation G169;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 guide covers elementary statistical methods for theanalysis of data common to weathering experiments.Themethods are for decision making,in which the experiments aredesigned to test a hypothesis on a single response variable.Themethods work for either natural or laboratory weathering.1.2 Only basic statistical methods are presented.There aremany additional methods which may or may not be applicableto weathering tests that are not covered in this guide.1.3 This guide is not intended to be a manual on statistics,and therefore some general knowledge of basic and interme-diate statistics is necessary.The text books referenced at theend of this guide are useful for basic training.1.4 This guide does not provide a rigorous treatment of thematerial.It is intended to be a reference tool for the applicationof practical statistical methods to real-world problems thatarise in the field of durability and weathering.The focus is onthe interpretation of results.Many books have been written onintroductory statistical concepts and statistical formulas andtables.The reader is referred to these for more detailedinformation.Examples of the various methods are included.The examples show typical weathering data for illustrativepurposes,and are not intended to be representative of specificmaterials or exposures.2.Referenced Documents2.1 ASTM Standards:2E41 Terminology Relating To ConditioningG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG141 Guide for Addressing Variability in Exposure Testingof Nonmetallic Materials2.2 ISO Documents:ISO 3534/1 Vocabulary and Symbols Part 1:Probabilityand General Statistical Terms3ISO 3534/3 Vocabulary and Symbols Part 3:Design ofExperiments33.Terminology3.1 DefinitionsSee Terminology G113 for terms relatingto weathering,Terminology E41 for terms relating to condi-tioning and handling,ISO 3534/1 for terminology relating tostatistics,and ISO 3534/3 for terms relating to design ofexperiments.3.2 Definitions of Terms Specific to This Standard:3.2.1 arithmetic mean;averagethe sum of values dividedby the number of values.ISO 3534/13.2.2 blocking variablea variable that is not under thecontrol of the experimenter,(for example,temperature andprecipitation in exterior exposure),and is dealt with byexposing all samples to the same effects3.2.2.1 DiscussionThe term“block”originated in agricul-tural experiments in which a field was divided into sections orblocks having common conditions such as wind,proximity tounderground water,or thickness of the cultivatable layer.ISO 3534/33.2.3 correlationin weathering,the relative agreement ofresults from one test method to another,or of one test specimento another.3.2.4 medianthe midpoint of ranked sample values.Insamples with an odd number of data,this is simply the middlevalue,otherwise it is the arithmetic average of the two middlevalues.3.2.5 nonparametric methoda statistical method that doesnot require a known or assumed sample distribution in order tosupport or reject a hypothesis.3.2.6 normalizationa mathematical transformation madeto data to create a common baseline.1This guide is under the jurisdiction of ASTM Committee G03 on Weatheringand Durability and is the direct responsibility of Subcommittee G03.93 on Statistics.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 2001.Last previous edition approved in 2008 as G169 01(2008)1.DOI:10.1520/G0169-01R13.2For 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.3Available from American National Standards Institute,11 W.42nd St.,13thFloor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.7 predictor variable(independent variable)a variablecontributing to change in a response variable,and essentiallyunder the control of the experimenter.ISO 3534/33.2.8 probability distribution(of a random variable)afunction giving the probability that a random variable takes anygiven value or belongs to a given set of values.ISO 3534/13.2.9 random variablea variable that may take any of thevalues of a specified set of values and with which is associateda probability distribution.3.2.9.1 DiscussionA random variable that may take onlyisolated values is said to be“discrete.”A random variablewhich may take any value within a finite o