ASTM E29-02
(Practice)Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
SCOPE
1.1 This practice is intended to assist the various technical committees in the use of uniform methods of indicating the number of digits which are to be considered significant in specification limits, for example, specified maximum values and specified minimum values. Its aim is to outline methods which should aid in clarifying the intended meaning of specification limits with which observed values or calculated test results are compared in determining conformance with specifications.
1.2 This practice is intended to be used in determining conformance with specifications when the applicable ASTM specifications or standards make direct reference to this practice.
1.3 Reference to this practice is valid only when a choice of method has been indicated, that is, either absolute method or rounding method.
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Standards Content (Sample)
Designation: E 29 – 02
Standard Practice for
Using Significant Digits in Test Data to Determine
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Conformance with Specifications
This standard is issued under the fixed designation E 29; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope example, the numbers 1270. and 32.00 each have four signifi-
cant digits. The significance of trailing zeros for numbers
1.1 This practice is intended to assist the various technical
represented without use of a decimal point can only be
committees in the use of uniform methods of indicating the
identified from knowledge of the source of the value. For
number of digits which are to be considered significant in
example, a modulus strength, stated as 140 000 Pa, may have
specification limits, for example, specified maximum values
as few as two or as many as six significant digits.
and specified minimum values. Its aim is to outline methods
3.1.2 To eliminate ambiguity, the exponential notation may
which should aid in clarifying the intended meaning of
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be used. Thus, 1.40 3 10 indicates that the modulus is
specification limits with which observed values or calculated
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reported to the nearest 0.01 3 10 or 1000 Pa.
test results are compared in determining conformance with
3.1.3 Use of appropriate SI prefixes is recommended for
specifications.
metric units to reduce the need for trailing zeros of uncertain
1.2 This practice is intended to be used in determining
significance. Thus, 140 kPa and 0.140 MPa each indicate that
conformance with specifications when the applicable ASTM
the modulus is reported to the nearest 1 kPa or 1000 Pa, while
specifications or standards make direct reference to this prac-
140 kPa may again have two or three significant digits.
tice.
1.3 Reference to this practice is valid only when a choice of
4. Significance and Use
method has been indicated, that is, either absolute method or
4.1 This practice describes two commonly accepted meth-
rounding method.
ods of rounding data, identified as the Absolute Method and the
2. Referenced Documents Rounding Method. In the applications of this practice to a
specific material or materials it is essential to specify which
2.1 ASTM Standards:
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method is intended to apply. In the absence of such specifica-
E 456 Terminology Relating to Quality and Statistics
tion, reference to this practice, which expresses no preference
SI 10 Standard for Use of the International System of Units
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as to which method should apply, would be meaningless. The
(SI) (the Modernized Metric System)
choice of method is arbitrary depending upon the current
3. Terminology
practice of the particular branch of industry or technology
concerned, and should therefore be specified in the prime
3.1 significant digit, n—any of the figures 0 through 9,
publication.
excepting leading zeros and some trailing zeros, which is used
4.1.1 The unqualified statement of a numerical limit, such as
with its place value to denote a numerical quantity to some
“2.50 in. max,” cannot, in view of different established
desired approximation.
practices and customs, be regarded as carrying a definite
3.1.1 The digit zero may either indicate a specific value or
operational meaning concerning the number of digits to be
indicate place only. Zeros leading the first nonzero digit of a
retained in an observed or a calculated value for purposes of
number indicate order of magnitude only and are not signifi-
determining conformance with specifications.
cant digits. For example, the number 0.0034 has two significant
4.1.2 Absolute Method—In some fields, specification limits
digits. Zeros trailing the last nonzero digit for numbers
of 2.5 in. max, 2.50 in. max, and 2.500 in. max are all taken to
represented with a decimal point are significant digits. For
imply the same absolute limit of exactly two and a half inches
and for purposes of determining conformance with specifica-
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This practice is under the jurisdiction of ASTM Committee E11 on Quality and
tions, an observed value or a calculated value is to be compared
Statistics and is the direct responsibility of Subcommittee E11.10 on Sampling and
directly with the specified limit. Thus, any deviation, however
Data Analysis.
Current edition approved May 10, 2002. Published July 2002. Originally small, outside the specification limit signifies nonconformance
published as E 29 – 40. Last previous edition E 29 – 93 (1999).
with the specifications. This will be referred to as the absolute
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Annual Book of ASTM Standards, Vol 14.02.
method, which is discussed in 5.
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Annual Book of ASTM Standards, Vol 14.04.
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