Variation Coefficient
The standard deviation discussed above is an absolute measure of dispersion. The corresponding relative measure is known as the coefficient of variation. This measure developed by Karl Pearson is the most commonly used measure of relative variation. It is used in such problems where we want to compare the variability of two or more than two series. That series (or group) for which the coefficient of variation is greater is said to be more variable or conversely less consistent less uniform less stable or less homogeneous. On the other hand the series for which coefficient of variation is less is said to be less variable or more consistent more uniform more stable or more homogeneous coefficient of variation is denoted by C.V and is obtained as follows.
Coefficient of variation or C.V. = s = X x 100
It may be pointed out that although any measure of dispersion can be used in conjunction with any average in computing relative dispersion statisticians in fact almost always use the standard deviation as the measure of dispersion and the arithmetic mean as the average. When the relative dispersion is stated inters of the arithmetic mean and the standard deviation the resulting percentage is known as the coefficient of variation or coefficient of variability.