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Coefficient of Variation (CV)
Coefficient of variation (below) is commonly used by age-reading labs in characterizing error in data. Chang (1982), and Kimura and Lyons (1991) both describe its application and promote its use. It is an unbiased estimate of error and incorporates the age range of the sample into the measure of precision. For example, error of a few years when the age range of the sample is 30-80 years old is less of a concern than if the range is 5-20 years old. Some species are quite difficult to read and a CV of .1 may be routine and acceptable while a CV of .1 for an easy to read species may be unacceptable. Easy to read species may have very low CV’s, for example, less than .03. Kimura and Lyons (1991) also characterize use of CV as simply describing the ease or difficulty in reading a species.
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(1) coefficient of variation
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Literature cited
Kimura, D. K., and J.L. Lyons. 1991. Between-reader bias and variability in the age-determination process. Fishery Bulletin 89:53-60
Chang, W.Y.B. 1982. A statistical method for evaluating the reproducibility of age determination. Canadian Journal of Fisheries and Aquatic Sciences, 39:1208-1210.
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