HFE has been estimated to be positive when it is on fact negative or vice versa), which is a more substantial misprediction than merely getting the value wrong by a certain amount. Such points lie to the left of the x = 0% axis (identified with a solid red line in Fig. ). In the case of a perfect predictor, all data points would stack at x = 100% (solid black line in Fig. ), i.e. the prediction perfectly matches experiment in sign and in magnitude. For x > 0% and x ≠ 100%, the predictor has correctly estimated the sign of the HFE, but not its magnitude, whereas for x < 0%, the HFE sign has been mispredicted. In terms of relative errors, the three water models have much more similar distributions with the three modes lying close to each other. Again, TIP3P has the tallest and narrowest distribution, with the second-tallest this time being OPC rather than OPC3, the latter two being very similar in shape and position. The TIP3P curve also has the smallest area lying to the left of x = 0%, i.e. TIP3P has the highest number of correctly predicted HFE signs (574/642), followed by OPC (547/642), and OPC3 (530/642).