14. Precision and Bias
14.1 The precision of this procedure as determined by the
statistical examination of the interlaboratory test results is as
follows:
14.2 Repeatability—The difference between results obtained on the same day by the same operator with the same
apparatus under constant operating conditions on identical test
material, would in the long run, with normal and correct
operation of the test method, exceed 1.76°C only in one case in
twenty.
14.3 Reproducibility—The difference between two single
and independent results obtained by different operators working in different laboratories on identical test material, would in
the long run, in the normal and correct operation of the test
method, exceed the values indicated by the formula:
0.102 (25−X)°C
where: X is the average of the two results being compared,
only in one case in twenty.
NOTE 11—The interlaboratory test program used to determine the
precision of this test method was carried out in 1988 by the IP. The
program involved 46 laboratories and 5 samples, ranging in CFPP values
from 0°C to −33°C. Extrapolations to measurements more than a few
degrees outside this range are unsupported by the data. The raw data from
the 1988 program was re-analyzed in 1997 using the ASTM D2PP
program. The report of the re-evaluation is available from ASTM
Headquarters RR:D02-1452.
14.4 Bias—The procedure in this test method has no bias
because the value of CFPP can be defined only in terms of a
test method.
14.5 Relative Bias—The current interlaboratory tests con-
firm that there is no relative bias between the manual and
automated apparatuses. Both apparatuses are suitable for reference purposes.