Dispersion of data is important.
In
Quality
field,
dispersion is important factor to succeed.

Standard deviation and variance ( square of standard deviation ) are useful
Statistical Value
to evaluate dispersion.

There is a case that standard deviation is larger as average is larger. In such case, standard deviation is not appropriate to evaluate.

Coefficient of variation is defined as

"Standard deviation / average"

This is useful to solve problem.

- Coefficient of variation is dimensionless quantity.
- Similar idea of coefficient of variation is in Dummy Variable and SN ratio of Quality Engineering

SN ratio series of Quality Engineering is also made to evaluate dispersion.

NEXT Standard Error