Since standard deviation, mean, median, and mode are all absolute data on statistical samples, they do not permit a direct comparison of variation between samples with different means or different units of measurement.
One way to obtain a measure of variation without units is to divide the standard deviation by the mean and multiply by 100 to give a percent. This quantity is called the coefficient of variation (CV) and can be used to compare methods with different units.
For example, the coefficient of variation for two different glucose methods would be calculated as shown below after the mean and standard deviation for each method have been established. The hexokinase method has a mean of 99 mg/dL and a standard deviation of 8.0 mg/dL. The orthotoluidine method has a mean of 105 mg/dL and a standard deviation of 12.5 mg/dL.
The lower the CV, the more precise (less variation) the method displays. From these CVs, we could conclude the hexokinase method is relatively more precise because it has a lower CV.
