PrIMe data: Uncertainty

Description

Every numerical value in PrIMe data records can have specified uncertainty (the exception are limiting values of physical properties for which given data record is valid, a.k.a. "valid range"; for example, lower and upper temperature and pressure for which particular chemcal model is applicable).

Probability distribution

The current structure of the uncertainty record assumes the uniform probability distribution within the specified limits.

Limits symmetry

The values for lower and upper uncertainty limits are specified separately, which allows for different upper and lower limits as, for example, in: E = 8.3 +0.1/-0.05 kJ/mol.

Limits values

The uncertainty limits can be specified as:

• Absolute values. Limits values have the same units as the property value, as in T = 1500 +/- 8 K;
• Values relative to the property value. The limit value is a (unitless) fraction of the property value, ranging from 0 to 1. For example, the mass flow controller may keep the flow rate within 2 % the set value throughout the controller's range. When the uncertainty limit is expressed relative to the property value, it can be provided relative to the value itself, or relative to the logarithm of the property value (either log-base-10 or ln).

Examples

For an example of reporting uncertainty, look at the plug flow experiment of Djurisic et al., 2004.