# Why are there 2 measures of LIBS performance used on this site - Detection Limit and RMSE?

The two measures attempt to answer different questions that are often asked about LIBS performance on a particular element.

Detection Limits are a measure of what the best performance of LIBS on a particular element in a given matrix might be.

Root Mean Square Error (RMSE) is given by:

\begin{aligned} RMSE = \sqrt{ \frac {\sum_{i=1}^n (concentration_{reference} - concentration_{measured})^2}{n}} \end{aligned}
It is provided as a measure of the routine or expected performance of LIBS for an element on a given matrix.
This is particularly important for Chemometric or Calibration Free methods, but is also a useful measure for standard univariate calibrations.