17.1 Comparison of Determined Values:
17.1.1 Determinability (d) - The difference between successive determined values obtained by the same operator in the same laboratory using the same apparatus for a series of operations leading to a single result, would in the long run, in the normal and correct operation of this test method, exceed the values indicated only in one case in twenty:
where: y is the average of determined values being compared.
17.2 Comparison of Results:
17.2.1 Repeatability (r) - The difference between successive results obtained by the same operator in the same laboratory 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 values indicated only in one case in twenty:
where: x is the average of results being compared.
17.2.2 Reproducibility (R) - The difference between two single and independent results obtained by different operators working in different laboratories on nominally identical test material would, in the long run, in the normal and correct operation of this test method, exceed the values indicated below only in one case in twenty.
where: x is the average of results being compared.
17.3 The precision for used oils has not been determined but is expected to be poorer than that fo rformulated oils. Because of the extreme variability of such used oils, it is not anticipated that the precision of used oils will be determined.
17.4 The precision for specific automated viscometers has not been determined. However, an analysis has been made of a large data set including both automated and manual viscometers over the temperature range of 40 to 100°C. The reproducibility of automated viscometer data is not statistically significantly different than the reproducibility of manual viscometer data. It is also shown that there is no bias of the automated data in comparison to the manual data.18. Keywords
18.1 dynamic viscosity; kinematic viscosity; viscometer; viscosity