It may surprise you to learn that there isn't actually a formal standard for how general-purpose measuring instruments are specified, or how those specifications are arrived at. Adequacy has often been judged by a relatively simple TAR approach considering only the principal accuracy spec. Although comprehensive in its treatment of the subject, it doesn't enjoy universal acclaim.
Statisticians say it is critically flawed.
Practicing engineers view it as too complicated and lengthy. It is, nevertheless, the first methodology to achieve formal, international consensus after decades of debate. ISO Practical Guides for Technicians Before, and after, release of the GUM several national guides have been produced which aim to provide practical advice for those equipment users who are more likely to be at technician, rather than scientist, level. The US National Institute of Standards and Technology published their own document to aid understanding of the ISO's, rather daunting, GUM . In outlining their policy and defining the practice for NIST's own staff, NIST Technical Note 1297 simplifies The Guide to 15 pages.