ASTM C670-96

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: C 670 – 96
Standard Practice for
Preparing Precision and Bias Statements for Test Methods
1
for Construction Materials
This standard is issued under the fixed designation C 670; 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 above and below the average) of a large group of individual
test results obtained under similar conditions.
1.1 This practice supplements Practice E 177, in order to
3.2.1 single-operator one-sigma limit—the one-sigma limit
provide guidance in preparing precision and bias statements for
for single-operator precision is a quantitative estimate of the
ASTM test methods pertaining to certain construction materi-
variability of a large group of individual test results when the
als (Note 1). Recommended forms for precision and bias
tests have been made on the same material by a single operator
statements are included. A discussion of the purpose and
using the same apparatus in the same laboratory over a
significance of these statements for the users of those test
relatively short period of time. This statistic is the basic one
methods is also provided.
used to calculate the single-operator index of precision given in
NOTE 1—Although under the jurisdiction of Committee C-9, this
the precision statement for guidance of the operator.
practice was developed jointly by Committees C-1, D-4, and C-9, and has
3.2.2 multilaboratory one-sigma limit—the one-sigma limit
been endorsed by all three committees. It has subsequently been adopted
for multilaboratory precision is a quantitative estimate of the
for use by Committee D-18.
variability of a large group of individual test results when each
2. Referenced Documents test has been made in a different laboratory and every effort has
been made to make the test portions of the material as nearly
2.1 ASTM Standards:
identical as possible. Under normal circumstances the esti-
C 109/C 109M Test Method for Compressive Strength of
mates of one-sigma limit for multilaboratory precision are
Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube
2
larger than those for single-operator precision, because differ-
Specimens)
ent operators and different apparatus are being used in different
C 802 Practice for Conducting an Interlaboratory Test Pro-
laboratories for which the environment may be different.
gram to Determine the Precision of Test Methods for
3
3.2.3 one-sigma limit in percent (1s%)—in some cases the
Construction Materials
coefficient of variation is used in place of the standard
E 177 Practice for Use of the Terms Precision and Bias in
4
deviation as the fundamental statistic. This statistic is termed
ASTM Test Methods
the “one-sigma limit in percent” (abbreviated (1s%)) and is the
3. Terminology
appropriate standard deviation (1s) divided by the average of
the measurements and expressed as a percent. When it is
3.1 Definitions of Terms Specific to This Standard:
appropriate to use (1s%) in place of (1s) is discussed in Section
3.2 one-sigma limit (1s)—the fundamental statistic underly-
6.
ing all indexes of precision is the standard deviation of the
3.3 Acceptable Range of Results:
population of measurements characteristic of the test method
3.3.1 acceptable difference between two results—the “dif-
when the latter is applied under specifically prescribed condi-
ference two-sigma limit (d2s)” or “difference two-sigma limit
tions (a given system of causes). The terminology “one-sigma
in percent (d2s%),” as defined in Practice E 177, has been
limit” (abbreviated (1s)) is used in Practice E 177 to denote the
selected as the appropriate index of precision in most precision
estimate of the standard deviation or sigma that is characteristic
statements. These indexes indicate a maximum acceptable
of the total statistical population. The one-sigma limit is an
difference between two results obtained on test portions of the
indication of the variability (as measured by the deviations
same material under the applicable system of causes described
in 4.1.1 and 4.1.2 (or whatever other system of causes is
1
This practice is under the jurisdiction of ASTM Committee C-9 on Concrete
appropriate). The (d2s) index is the difference between two
and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.94on
individual test results that would be equaled or exceeded in the
Evaluation of Data.
Current edition approved May 10, 1996. Published July 1996. Originally long run in only 1 case in 20 in the normal and correct
published as C 670 – 71 T. Last
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