Quandaries and Queries
I am currently teaching the coefficient of variation and am wondering if there are some guidelines as to the interpretation of this statistic. I understand that it measures the variation in a variable relative to the mean – but what is the cut off for “too much” variation expressed in this way???
The coefficient of variation expresses the standard deviation as a percentage of the sample mean. This is useful when interest is in the size of variation relative to the size of the observation, and it has the advantage that the coefficient of variation is INDEPENDENT OF the UNITS of observation. For example, the value of the standard deviation of a set of weights will be different depending on whether they are measured in kilograms or pounds. The coefficient of variation, however, will be the same in both cases as it does not depend on the unit of measurement.
A value for saying there is too much variation seems to be subject dependent. In an Internet search we found three applications with different values.
An application to sports has the statement
A site about llamas, Llamapaedia has a page on fiber testing which contains the sentence about the coefficient of variation
And a page Statistics for Microarray Analysis which says for their application the user can set the value and then gives examples of 3% and 5%.
Andrei and Penny