Uncertainties listed in all tables and output files of the ThermoData Engine software represent estimates of the Combined Expanded Uncertainty (with 95% Level of Confidence) for the property value.

The Combined Expanded Uncertainty and Level of Confidence are defined in the article:

The definitions are in accord with those provided in the U. S. Guide to the Expression Of Uncertainty in Measurement, which is also known as the GUM. Complete references are provided in the article listed above.