When to use coefficient of variance

• When comparison groups have very different
  means (CV is suitable as it expresses the standard
  deviation relative to its corresponding mean)


• When different units of measurements are
  involved, e.g. group 1 unit is mm, and group 2 unit
  is mg (CV is suitable for comparison as it is unit-
  free)


• In such cases, standard deviation should not be
  used for comparison