Index of Ideality of Correlation: new possibilities to validate QSAR: a case study

New criterion of the predictive potential of quantitative structure - property/activity relations (QSPRs/QSARs) named Index of Ideality of Correlation (IIC) is suggested. This criterion is calculated using the correlation coefficient between experimental and calculated values of an endpoint for the calibration set, taking into account positive and negative differences between experimental and calculated values of the endpoint. Using this criterion improves the predictive potential of QSAR models of toxicity towards fathead minnow (Pimephales promelas). Comparison of IIC with other metrics of predictive potential shows that (i) the IIC is not identic to other metrics; and (ii) the IIC seems more reliable criterion at least for examined data on toxicity towards fathead minnow.