Table . A summary of the squared correlation coefficient (R 2 ), root mean square error (RMSE), and mean unsigned error (MUE) for ln γ ∞ i,j , and the average absolute percent deviation (AAPD) for γ ∞ i,j predicted using the SM12, SM8, and SMD universal solvent model as compared to the reference data from the Minnesota Solvation Database. For the predictions, we compare the case where 1) ∆G self i,i is predicted using the SM12, SM8, and SMD universal solvent model, and where 2) ∆G self i,i is computed using reference data, as indicated. Again, while the difference in the two sets of predictions does not appear to be large, in all cases we find that R 2 increases and the computed overall errors decrease when using reference values of ∆G self i,i . One might expect this result. Consider eq. ( ) and the errors summarized in tables 1 to 3, where we will take RMSE as a measure of the error in the predictions. When using reference values of ∆G self i,i , the only predicted quantity in eq. ( ) is ∆G solv i,j . As a result, we find for this case that the RMSE for the predicted values of ln γ ∞ i,j is identical to that for ∆G solv i,j / (RT). Next, consider the case of when ∆G self i,i is predicted. Using propagation of error, we would expect the error (taken to be RMSE) in ln γ ∞ i,j to be equal to RMSE 2 solv + RMSE 2 self , where RMSE solv and RMSE self are the RMSE for the predicted values of ∆G solv i,j / (RT) and ∆G self i,i / (RT), respectively. This would result in an RMSE of 1.893, 1.970, and 2.170 for SM12, SM8 and SMD, respectively. However, we find that the actual error is less than the predicted error. The expression used assumes that the error is random . The smaller observed uncertainty suggests the presence of systematic error.