ASTM D6618 Standard Test Method for Evaluation of Engine Oils in Diesel Four-Stroke Cycle Supercharged 1M-PC Single Cylinder Oil Test Engine
13. Precision and Bias
13.1 Test precision is established on the basis of reference oil test results (for operationally valid tests) monitored by the ASTM Test Monitoring Center. The data are reviewed semi-annually by the Single-Cylinder Diesel Surveillance Panel. Contact the ASTM TMC for current industry data.
13.1.1 Table 11 summarizes reference oil intermediate precision and reproducibility of the test. The tabulated values are current as of Feb.1, 2005. The Surveillance Panel updates these values as necessary.
13.1.2 Intermediate Precision Conditions - Conditions where test results are obtained with the same test method using the same test oil, with changing conditions such as operators, measuring equipment, test stands, test engines, and time.
NOTE 4 - Intermediate precision is the appropriate term for this test method rather than repeatability which defines more rigorous within-laboratory conditions.
13.1.2.1 Intermediate Precision Limit (i.p.) - The difference between two results obtained under intermediate precision conditions that would, in the long run, in the normal and correct conduct of the test method, exceed the values shown in Table 11 in only one case in twenty. When only a single test result is available, the Intermediate Precision Limit can be used to calculate a range (test result +/- Intermediate Precision Limit) outside of which a second test result would be expected to fall about one time in twenty.
13.1.3 Reproducibility Conditions - Conditions where test results are obtained with the same test method using the same test oil in different laboratories with different operators using different equipment.
13.1.3.1 Reproducibility Limit (R) - The difference between two results obtained under reproducibility conditions that would, in the normal and correct conduct of the test method, exceed the values shown in Table 11 in only one case in twenty. When only a single test result is available, the Reproducibility Limit can be used to calculate a range (test result +/- Reproducibility Limit) outside of which a second test result would be expected to fall about one time in twenty.
13.2 Bias - Bias is determined by applying an acceptable statistical technique to reference oil test results, and when a significant bias is determined, a severity adjustment is permitted for non-reference oil test results (see TMC Memorandum 94-200, Lubricant Test Monitoring System document for details).
14. Keywords
14.1 1M-PC; diesel engines; heavy-duty performance; ring belt deposits; single cylinder test
