Topic summary
RMSE

Extracted from the Wikipedia article Root mean square deviation.
The root mean square deviation (RMSD) or root mean square error (RMSE) is a frequently used measure of the distances between actual observed values and an estimation of them (e.g. true/predicted in regression tasks of Machine learning). The deviation is typically simply a differences of scalars; it can also be generalized to the vector lengths of a displacement, as in the bioinformatics concept of root mean square deviation of atomic positions.