In the case the final uncertainty remains asymmetric, the authors should provide detailed information about the `shape of the uncertainty', giving also most probable value, probability intervals, and so on. But the best estimate of the expected value and standard deviation should be always given (see also the ISO Guide ).
To conclude, I would like to leave the final word to my preferred quotation with whom I like to end seminars and courses on probability theory applied to the evaluation and the expression of uncertainty in measurements:
provides a framework for assessing uncertainty, it cannot substitute for critical thinking, intellectual honesty, and professional skill. The evaluation of uncertainty is neither a routine task nor a purely mathematical one; it depends on detailed knowledge of the nature of the measurand and of the measurement. The quality and utility of the uncertainty quoted for the result of a measurement therefore ultimately depend on the understanding, critical analysis, and integrity of those who contribute to the assignment of its value.''
It is a pleasure to thank Superfaber (Fabrizio Fabbri in hepnames) for helpful discussions on the subject and for his supervision of the manuscript.