ASTM G169-01(2013)
(Guide)Standard Guide for Application of Basic Statistical Methods to Weathering Tests
Standard Guide for Application of Basic Statistical Methods to Weathering Tests
SIGNIFICANCE AND USE
4.1 The correct use of statistics as part of a weathering program can greatly increase the usefulness of results. A basic understanding of statistics is required for the study of weathering performance data. Proper experimental design and statistical analysis strongly enhances decision-making ability. In weathering, there are many uncertainties brought about by exposure variability, method precision and bias, measurement error, and material variability. Statistical analysis is used to help decide which products are better, which test methods are most appropriate to gauge end use performance, and how reliable the results are.
4.2 Results from weathering exposures can show differences between products or between repeated testing. These results may show differences which are not statistically significant. The correct use of statistics on weathering data can increase the probability that valid conclusions are derived.
SCOPE
1.1 This guide covers elementary statistical methods for the analysis of data common to weathering experiments. The methods are for decision making, in which the experiments are designed to test a hypothesis on a single response variable. The methods work for either natural or laboratory weathering.
1.2 Only basic statistical methods are presented. There are many additional methods which may or may not be applicable to 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 intermediate statistics is necessary. The text books referenced at the end of this guide are useful for basic training.
1.4 This guide does not provide a rigorous treatment of the material. It is intended to be a reference tool for the application of practical statistical methods to real-world problems that arise in the field of durability and weathering. The focus is on the interpretation of results. Many books have been written on introductory statistical concepts and statistical formulas and tables. The reader is referred to these for more detailed information. Examples of the various methods are included. The examples show typical weathering data for illustrative purposes, and are not intended to be representative of specific materials or exposures.
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: G169 − 01 (Reapproved 2013)
Standard Guide for
Application of Basic Statistical Methods to Weathering
1
Tests
This standard is issued under the fixed designation G169; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ISO Documents:
ISO 3534/1 Vocabulary and Symbols – Part 1: Probability
1.1 This guide covers elementary statistical methods for the
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and General Statistical Terms
analysis of data common to weathering experiments. The
ISO 3534/3 Vocabulary and Symbols – Part 3: Design of
methods are for decision making, in which the experiments are
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Experiments
designedtotestahypothesisonasingleresponsevariable.The
methods work for either natural or laboratory weathering.
3. Terminology
1.2 Only basic statistical methods are presented. There are
3.1 Definitions—See Terminology G113 for terms relating
many additional methods which may or may not be applicable
to weathering, Terminology E41 for terms relating to condi-
to weathering tests that are not covered in this guide.
tioning and handling, ISO 3534/1 for terminology relating to
1.3 This guide is not intended to be a manual on statistics,
statistics, and ISO 3534/3 for terms relating to design of
and therefore some general knowledge of basic and interme-
experiments.
diate statistics is necessary. The text books referenced at the
3.2 Definitions of Terms Specific to This Standard:
end of this guide are useful for basic training.
3.2.1 arithmetic mean; average—the sum of values divided
1.4 This guide does not provide a rigorous treatment of the
by the number of values. ISO 3534/1
material.Itisintendedtobeareferencetoolfortheapplication
3.2.2 blocking variable—a variable that is not under the
of practical statistical methods to real-world problems that
control of the experimenter, (for example, temperature and
arise in the field of durability and weathering. The focus is on
precipitation in exterior exposure), and is dealt with by
the interpretation of results. Many books have been written on
exposing all samples to the same effects
introductory statistical concepts and statistical formulas and
3.2.2.1 Discussion—The term “block” originated in agricul-
tables. The reader is referred to these for more detailed
information. Examples of the various methods are included. tural experiments in which a field was divided into sections or
blocks having common conditions such as wind, proximity to
The examples show typical weathering data for illustrative
purposes, and are not intended to be representative of specific underground water, or thickness of the cultivatable layer.
ISO 3534/3
materials or exposures.
3.2.3 correlation—in weathering, the relative agreement of
2. Referenced Documents
resultsfromonetestmethodtoanother,orofonetestspecimen
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2.1 ASTM Standards:
to another.
E41 Terminology Relating To Conditioning
3.2.4 median—the midpoint of ranked sample values. In
G113 Terminology Relating to Natural andArtificial Weath-
samples with an odd number of data, this is simply the middle
ering Tests of Nonmetallic Materials
value, otherwise it is the arithmetic average of the two middle
G141 Guide for Addressing Variability in Exposure Testing
values.
of Nonmetallic Materials
3.2.5 nonparametric method—a statistical method that does
not require a known or assumed sample distribution in order to
support or reject a hypothesis.
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This guide is under the jurisdiction of ASTM Committee G03 on Weathering
andDurabilityandisthedirectresponsibilityofSubcommitteeG03.93onStatistics.
3.2.6 normalization—a mathematical transformation made
Current edition approved June 1, 2013. Published June 2013. Originally
ε1 to data to create a common baseline.
approved in 2001. Last previous edition approved in 2008 as G169 – 01 (2008) .
DOI: 10.1520/G0169-01R13.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on Available from American National Standards Institute, 11 W. 42nd St., 13th
the ASTM website. Floor, New York, NY 10036.
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G169 − 01 (2013)
3.2.7 predictor variable (independent variable)— a variable thought of as the probability of rejecting the null hypothesis
contributing to change in a response variable, and essentially when it is really true (that is, the chance of making such an
under the control of the e
...
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