11. Precision and Bias
11.1 Precision - The following criteria should be used for judging acceptability of results (95% probability) for lubricating fluids which follow the compensation line and have weld points of 400kg or less.
11.1.1 Load-Wear Index:
11.1.1.1 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, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
17% of the mean value
11.1.1.2 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, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
44% of the mean value
11.1.2 Weld Point:
11.1.2.1 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, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
more than one increment loading
11.1.2.2 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, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
more than one increment loading
NOTE 14 - A round robin with five cooperators has shown that at a 95% confidence level similar load-wear index and weld point values have been obtained with five lubricants at 1770rpm (two laboratories) and at 1440rpm (three laboratories). Physical properties and composition of the lubricating fluids used and sample data obtained by this round-robin testing are shown in the appendix.
11.2 Precision for lubricants with weld points greater than 400kg or above the compensation line, or both, has not been established.
11.3 Bias - Since there is no accepted reference material suitable for determining the bias for the procedure in this Test Method D2783, no statement on bias is being made.
12. Keywords
12.1 extreme pressure properties (in lubricating fluids); load wear index; weldpoint
