12. Calculation and Report
12.1 Correct the readings at the upper and lower oil surfaces in accordance with the calibration error.
12.2 Calculate the unsulfonated residue as follows:
Unsulfonated residue, volume % = [(A - B)/V] x 100
where:
A = corrected scale reading, at upper oil level, mL,
B = corrected scale reading at lower oil level, mL, and
V = volume of sample used, mL.
12.3 Report all results to the nearest 0.2 %.
13. Precision and Bias
13.1 The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
13.1.1 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:
13.1.2 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 one case in twenty:
13.2 The precision of this test method is not known to have been obtained in accordance with currently accepted guidelines.
13.3 Bias - There being no criteria for measuring bias in these test product combinations, no statement of bias can be made.
14. Keywords
14.1 petroleum plant spray oils; unsulfonated residue