24. Precision and Bias
24.1 The precision of these test methods as obtained by statistical examination of interlaboratory test results is as follows:
24.1.1 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, in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
24.1.2 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:
NOTE 12 - The precision of the analyses are based on the use of tetraethyl lead standards only, and users of the test method are cautioned that the precision of the analyses using other lead containing standards may not apply.
24.2 Bias - A result from these test methods does not differ from the actual value by more than the reproducibility of the test methods.
NOTE 13 - The bias was determined from analysis of NIST reference materials by four laboratories.
25. Keywords
25.1 gasoline; lead; low lead; TEL, tetraethyllead; X-ray; X-ray fluorescence