13. Report
13.1 In reporting density, give the test temperature and the units, (for example: density at 20°C = 0.8765 g/mL or 876.5 kg/m3 (in vacuo)).
13.2 In reporting relative density, give both the test temperature and the reference temperature, but no units, (for example: relative density, 15/15°C = x.xxxx).
13.3 Report the final result to four significant figures.
14. Precision and Bias
14.1 The precision of this test method as obtained by statistical examination of interlaboratory test results at test temperatures of 15 and 20°C is as follows:
14.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of this test method, exceed the following value only in 1 case in 20 (see Table 2):
where:
X = sample mean.
14.1.2 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 following values only in 1 case in 20 (see Table 2):
where:
X = sample mean.
14.2 Bias - After suggestions of its existence from literature,7 a study has been performed which has confirmed the presence of a bias between known density values for reference materials and from values determined according to this test method on the same reference materials. The matrix for this bias study was comprised of 15 participants, each analyzing four reference oils with certified density values, established by the Netherlands Meet Instituut (NMI), by pycnometry, covering densities in the range of 747 to 927 kg/m3 at 20°C, with viscosities between 1 and 5000 mPa.s (also at 20°C). Users should, therefore, be aware that results obtained by this test method can be biased by as much as 0.6 kg/m3(0.0006 g/mL).
15. Keywords
15.1 crude oils; density; digital density analyzer; relative density