# Relative Standard Deviation (RSD) of more than 100%

Relative standard deviation (RSD) is defined as:

$$RSD = \frac{100 \times s}{\overline{x}}$$

where $s$ is the standard deviation and $\overline{x}$ is the mean.

How should a RSD of 170% for a mean of 0.002 be interpreted. I am guessing it means that the values are not clustered tightly but I am not sure.

It can be assumed that all $X$ are positive for the calculations I am doing. $X$ is the predicted contributions (value between 0 and 1) of a contaminant from some source to an environment.

• Is the variable, $X$ necessarily positive? – Glen_b Oct 10 '17 at 2:45
• This measure is also called the coefficient of variation (more frequently, in my experience). That's not just terminology: the corresponding tag, now edited in to the question, leads to several discussions of this sometimes oversold measure. – Nick Cox Oct 10 '17 at 14:20