The Definition of Precision and Bias on Standard Test Method in materials

ChemicalFormulas - On This page we want to discuss about the definition of Precision and Bias, that is usually faced by the chemist if doing Standard Test at chemical laboratory.

Precision—The precision of this test method as determined by statistical examination of interlaboratory results is as follows:

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: 0.8°C (1.4°F)

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: 1.3°C (2.4°F)

NOTE 3

The following information on the precision of this test method was developed by the Institute of Petroleum (now Energy Institute) in London and is being investigated:

(1) Results of duplicate tests should not differ by more than the following amounts:

Repeatability	Reproducibility
1°C (2°F)	1.2°C (2.2°F)

(2) These precision values were obtained in 1954 by statistical examination of interlaboratory test results.

Bias—The procedure in this test method has no bias because the value of drop melting point can be defined only in terms of a test method.