This text is a summary from the Supporting Opinion of the Uncertainty Analysis Guidance SO 8
Some assessments require only some elements, and each element can be implemented in various ways with various methods.
What is needed depends in part on the general type of the assessment
and partly on the specific needs of the individual assessment, which need to be decided by assessors.
This is necessary in every assessment, and should be done in a structured way to minimise the chance of overlooking relevant uncertainties. In assessments that follow standardised procedures, it is only necessary to identify non-standard uncertainties.
Source of uncertainty
An individual contribution to uncertainty
Always necessary
This is necessary in every assessment, and should be done in a structured way to minimise the chance of overlooking relevant uncertainties.
Generic lists
It is useful to develop generic lists of standard and non-standard uncertainties.
Standardised procedures
In assessments that follow standardised procedures, it is only necessary to identify non-standard uncertainties.
Plays an important role in the planning the uncertainty analysis, enabling the assessor to focus detailed analysis on the most important uncertainties and address others collectively when evaluating overall uncertainty. Often prioritisation will be done by expert judgement during the planning process, but in more complex assessments it may be done explicitly, using influence or sensitivity analysis.
In some assessments, it may be sufficient to characterise overall uncertainty for the whole assessment directly, by expert judgement. In other cases, it may be preferable to evaluate uncertainty for some or all parts of the assessment separately and then combine them, either by calculation or expert judgement.
This is necessary in every assessment. Some assessments follow standardised procedures, within which the questions and/or quantities of interest should be predefined. In other assessments, the assessors will need to identify and define the questions and/or quantities of interest case by case.
This is needed for assessments where the assessors choose to divide the uncertainty analysis into parts, but may only be done for some of the parts, with the other parts being considered when characterising overall uncertainty.
This is needed for assessments where the assessors quantify uncertainty separately for two or more parts of the uncertainty analysis.
Expressing quantitatively the overall impact of as many as possible of the identified uncertainties, and describing qualitatively any that remain unquantified. This is necessary in all assessments except standardised assessments where no non-standard uncertainties are identified.
This is implicit or explicit in any assessment where recommendations are made for future data collection or research, and may be informed by influence or sensitivity analysis.
Required for all assessments, but extremely brief in standardised assessments where no non-standard uncertainties are identified.