Geometric mean:
The geometric mean of n values is determined by multiplying all n values together, then taking the nth root of the product. It is useful in taking averages of ratios.
The geometric mean is often used for data which take only on positive values and the values can vary significantly - e.g. by orders of magnitude. An example of such data in biomedical applications is the concentration of various substances in blood and other body fluids.
See also: geometric mean and mean (comparison) .