ASME (2005) Standard

• A revision of ASME (1998) Standard

• Main revision is focused on the harmonization with the ISO Guide (1995) which utilizes conceptually different error/uncertainty classifications (Type A and Type B).

• The terms 'bias' and 'precision' are not used

• Uncertainties remain conceptualized as 'systematic' and 'random'

• The term 'standard' uncertainty is introduced.

• The terms such as 'combined standard' uncertainty and 'expanded' uncertainty are used instead of the 'total' uncertainty.

For a result, R, of which DRE is given as

• Systematic standard uncertainty is determined from the error propagation equation as

where

• Random standard uncertainty of the mean result from M repeat tests is

• Combined standard uncertainty is the root-sum-square of b_R and s_R as

• Expanded uncertainty is the expanded u_R to the 95% confidence level by multiplying an appropriate expansion factor t₉₅ as

• The expansion factor t₉₅ = 2 for large degree of freedom ν_R > 30.  When the degree of freedom for one of the b_R and s_R, or for both, is not large (ν_R < 30), an effective degree of freedom is obtained by using the Welch-Satterthwaite formula (Nonmandatory Appendix B).