Components kept separate, in the value's unit (literature SCHEMA.md, UNCERTAINTY_CALIBRATION.md): effective = max(sqrt(max(printed, reading, method)^2 + composition^2 + conversion^2), scatter). The method floor is the robust between-study scatter of the method class in ORCHID (calibrated) or a documented prior; printed values and printed uncertainties are unchanged.
Uncertainty budget of the literature values of Al2Mg
Value
Unit
Printed
Reading
Method (class, basis)
Composition
Scatter
Conversion
Effective
-2.802
kJ/mol-atom
5.000e-4
8.395 (dft, calibrated)
8.395
-2.713
kJ/mol-atom
5.000e-4
8.395 (dft, calibrated)
8.395
-2.301
kJ/mol-atom
5.000e-4
8.395 (dft, calibrated)
8.395
Sources
Yu Zhong, Mei Yang, Zi-Kui Liu, Contribution of first-principles energetics to Al–Mg thermodynamic modeling, Calphad 29, 303-311 (2005). doi:10.1016/j.calphad.2005.08.004