The coefficient of variation of the mean (CV_{mean}) is the standard error of the mean expressed as a percentage of the mean. It has a variety of other names including the relative standard error.
It provides a measure of an estimate's reliability. It should be clearly distinguished from the coefficient of variation of the individual measurements which is the standard deviation expressed as a percentage of the mean.
Algebraically speaking 
Coefficient of Variation of the Mean (%) 
= 
100 × SE 


 = 
100  ×  s 

 ×  √n 
where:
 SE is the standard error of the mean,
 s is the standard deviation of the observations,
 n is the number of observations comprising each sample.

It is mainly used to estimate the required sample size for a given coefficient of variation. If the coefficient of variation of the mean is plotted against sample size, the coefficient of variation will decline to an asymptote as sample size increases. An example of this is given in one of our wildlife examples.