Precision of calculated equilibria

If we can accurately calculate an equilibrium at P and T, why should we care about its precision The reason of course is 

If we are calculating the temperature of an equilibrium assemblage given the pressure on the system, there are four main factors which govern the precision attached to that temperature. 

The precision of the free energy or enthalpy of the mineral phases (free energies are used with the constant AS method, enthalpies with the heat capacity method see equations in Appendix 1) The precision of the entropies is often a significant but smaller factor. Since these appear in a TAS term, they are more significant the higher the temperature. 

The degree of correlation or covariance between the free energies or enthalpies of the minerals. 

Each of these factors is highly significant, the net result being controlled by their interaction. Before considering them, 

---