Q2 Statistic

The QSARs obtained were then tested by cross validation and visual examination of plots of fitted values against residuals. Cross-validation was performed by leave-one-out (LOO) testing. Each data point was omitted in turn from a regression, and the actual value of the omitted point compared to the value predicted by the revised model. The difference was referred to as a deletion residual. Q2 values (an analog of the summary statistic R2) were then calculated from the sum of squares of the deletion residuals. The Q2 statistic provides a measure of the predictive power of a regression, and is therefore more relevant for QSAR modeling than the R2 statistic (Damborsky and Schultz, 1997). 

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