CIAAW gives the representative abundance of oxygen-16 in normal materials as the interval [0.99738, 0.99776], reflecting real variation between materials rather than measurement uncertainty.
- method: Critical evaluation of published isotopic composition measurements by CIAAW.
- precision note: An interval because the natural composition varies; not an uncertainty on a single value.
Evidence support: Supported by the cited evidence one source
Evidence: Commission on Isotopic Abundances and Atomic Weights (IUPAC) 2024 Primary authority