After several weeks of silence, we have another proposal about QSAR validation , based on mean absolute error (MAE) and its standard deviation. And this article  is a starting point for further lecture, if it is not known for the reader (more than 1800 citations).
- K. Roy, R.N. Das, P. Ambure, and R.B. Aher, "Be aware of error measures. Further studies on validation of predictive QSAR models", Chemometrics and Intelligent Laboratory Systems, vol. 152, pp. 18-33, 2016. http://dx.doi.org/10.1016/j.chemolab.2016.01.008
- A. Golbraikh, and A. Tropsha, "Beware of q2!", Journal of Molecular Graphics and Modelling, vol. 20, pp. 269-276, 2002. http://dx.doi.org/10.1016/S1093-3263(01)00123-1