The Coefficient of Variation (CV) is a commonly reported measure of repeatability generally used in all pathology assays. It is derived from the Standard Deviation by dividing the SD by the mean of the repeated measures and multiplying by 100.
Coefficient of Variation (CV) = (Standard Deviation / Mean) * 100
It is also known as the relative standard deviation as it describes the standard deviation as a function of the average (mean) of the measurements made.
Although this may be used in calculations for the Top-Down method of uncertainty evaluation in pathology, it is not customary to use the CV as a measure of standard uncertainty, although it is useful in determining the imprecision of an assay at a given time. Instead it is more appropriate to use the standard deviation, assuming a normal distribution of data is observed.