The coefficient of variation is a relative measure of the dispersion of data points around the mean. Calculated as the ratio of the standard deviation divided by the mean expressed as a percentage, the coefficient of variation can be used to compare the degree of variation from one sample to another, even if the means are different.

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where s is the sample standard deviation and is the sample mean.

When the standard deviation and mean come from repeated measurements of a single subject, (e.g., an athlete’s performance in different competitions) the resulting coefficient of variation is an important measure of reliability.