10. Precision and Bias
10.1 The precision of this test method is not known to have been obtained in accordance with currently accepted guidelines (for example in Committee D02 research report RR: D02 1007, "Manual on Determining Precision Data for ASTM Methods on Petroleum Products and Lubricants").
10.2 The precision of the test method (Note 2) as determined by statistical examination of interlaboratory results is as follows:
NOTE 2 - The criteria for repeatability and reproducibility are based on the spread in the numbers after conversion to the full-scale units described in Test Methods D1403. Precision of this test method was established using the one-quarter scale equipment, but based on the precision values in Test Methods D1403, the precision of this test should be at least as good or better using the one-half scale equipment.
10.2.1 Repeatability - The difference between two 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 the test method, exceed the following values only in one case in twenty:
Range of Sample Repeatability
NLGI Consistency Nos.1 and 2 11 penetration units - tenths of a millimetre
10.2.2 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, in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
Range of Sample Reproducibility
NLGI Consistency Nos.1 and 2 45 penetration units - tenths ofa millimetre
10.3 Bias - The procedure in Test Method D1831 has no bias because the value of the change in penetration can be defined only interms of a test method.
11. Keywords
11.1 cone penetration; consistency; lubricating grease; penetration; roll stability; shear stability
