CPB Ljubljana 2018 course book

Definition of Uncertainty: Types of Uncertainty

Expanded uncertainty is the standard uncertainty multiplied by a coverage factor , k , such that the statement of the expanded uncertainty gives a higher probability that the correct value lies within the range of the stated uncertainty .

Often the expanded uncertainty is given the symbol U such that

U = k u

Generally k > 1 .

For k equal to 1, 2, or 3, there is approximately a 67%, 95%, or 99% probability, respectively, that the true value lies between ± U of the measured mean value . Often we will see uncertainties quoted, for example, “at the k 2 level” or “with k = 2”.

Accuracy and Uncertainty Considerations in Modern Radiation Oncology, The Modern Technology of Radiation Oncology, J. Van Dyk, 2013