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Definition of Uncertainty: Types of Uncertainty
Uncertainty
is a parameter that characterizes the dispersion of values that can be
obtained for a particular measurement when it is performed repeatedly. For such
repeated measurements, the results can be represented by a statistical distribution,
which can be summarized by specific statistical quantities such as mean, mode,
standard deviation, and variance.
Standard uncertainty
is the standard deviation. The symbol often attributed to the
standard uncertainty is u.
Combined standard uncertainty
is the standard uncertainty of a quantity that is
composed of various components, each of which has its own uncertainty. The combined
standard uncertainty is obtained by combining the square of the sums of the individual
standard deviations and taking the square root. This assumes a gaussian distribution for
each of the contributing uncertainties. This mathematical procedure for combining
uncertainties is generally known as “addition in quadrature.”
Accuracy and Uncertainty Considerations in Modern Radiation Oncology,
The Modern Technology of Radiation Oncology, J. Van Dyk, 2013